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gricuiiuralCuemis 


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PRACTICAL 

AGRICULTURAL    CHEMISTRY 

FOR    ELEMENTARY     STUDENTS 
ADAPTED  FOR  USE  IN  AGRICULTURAL  CLASSES  AND  COLLEGES 

BY 

J.   BERNARD    COLEMAN,   A.R.C.Sc,   F.I.G. 

HEAD  OF  THE  CHEMICAL  DEPARTMENT,  SOUTH   WESTERN   POLYTECHNIC,  CHELSEA,  S.W 
FORMERLY  LECTURER  ON   THE  PRINCIPLES  OF  AGF&CltLi^ltB!  *.    .*  , 

IN   THE   UNIVERSITY  COLLEGE,    NOTTINGHAM-      •    *•    "        •      • 


«  •       *         •••••••   "•   ••    •    • 

and  .     ••  ;    :  :• .  :• .  •*.•: ; 


FRANK  T.  ADDYMAN,  B.Sc.  (Lond.),  F.I.C. 

CONSULTING  CHEMIST,  FORMERLY  ASSISTANT  IN  THE  LABORATORY  OF 

THE  ROYAL  AGRICULTURAL  SOCIETY  OF  ENGLAND 

LATE  PRINCIPAL  OF  THE  LANCASHIRE  COUNTY  SCHOOL  OF  AGRICULTURE 


NEW  IMPRESSION 


LONGMANS,     GREEN,    AND    CO. 

39   PATERNOSTER   ROW,  LONDON 

NEW   YORK,    BOMBAY,   AND   CALCUTTA 

1913 

All   rights   reserved 


.•  • 8  .•• 


•••iflN  LIBRARY-AGRICULTURE  DEFT. 


PREFACE 


The  course  of  instruction  described  in  this  book  was  origi- 
nally arranged  for  the  students  of  agriculture  at  University 
College,  Nottingham. 

It  is  now  largely  used  by  the  teachers  and  students  of 
the  numerous  agricultural  classes  established  throughout 
the  country. 

It  is  suited  to  the  requirements  of  those  commencing 
the  study  of  Agriculture. 

The  experiments  are  so  arranged  as  to  give  a  scientific 
acquaintance  with  the  substances  commonly  met  with  on 
the  farm. 

The  matter  is  divided  into  the  following  sections  :— 

Section  I.  treats  of  simple  chemical  manipulation  and 
the  preparation  of  apparatus. 

Section  II.  describes  the  preparation  and  properties  of 
the  constituents  of  air  and  water. 

Section  III.  contains  a  number  of  experiments  illus- 
trating the  properties  of  soils,  manures,  feeding  materials, 
and  dairy  produce. 

Section  IV.  gives  the  chemical  tests  for  the  bodies 
commonly  occurring  in  soils,  manures,  and  ashes  of  plants, 
and  describes  the  qualitative  analysis  of  these  bodies. 

It  will  be  seen  that  only  those  substances  are  treated  of 


469651 


iv  PRACTICAL  AGRICULTURAL  CHEMISTRY 

that  enter  into  the  composition  of  the  various  agricultural 
products.  For  the  analyses  of  minerals  and  other  occa- 
sional constituents  found  in  the  earth,  works  on  qualitative 
analysis  should  be  consulted. 

Section  V.  contains  a  list  of  apparatus  and  chemicals 
lequired  for  performing  the  experiments  described  in  this 
book,  together  with  instructions  for  preparing  the  various 
solutions. 

After  working  through  this  course,  students  are  recom- 
mended to  consult  Addyman's  '  Agricultural  Analysis.' 

Our  acknowledgments  are  due  to  Professor  F.  Clowes, 
D.Sc.  (Lond.),  for  permission  to  use  woodcuts  and  other 
material  from  his  text-book  on  Qualitative  Analysis. 

In  the  preparation  of  the  present  edition,  the  whole  of 
the  existing  matter  has  been  carefully  revised.  Some  por- 
tions have  been  re-written  and  important  additions  have 
been  made. 

J.  B.  C. 
F.  T.  A. 

London  :  Oct.  1908. 


CONTENTS 


SECTION   I 

CHEMICAL  MANIPULATION  AND 
APPARATUS 

PARA-  PAG1 
GRAPH 

The  Bunsen  Burner i  i 

The  Spirit  Lamp 2  2 

The  Blowpipe 3  2 

The  Table  Blowpipe .4  3 

Cutting  and  Bending  Glass  Tube  and  Rod     .          5  3 

Making  Closed  Tubes 6  4 

Mounting  Platinum  Wire 7  4 

Boring  Corks .     .      8-9  5 

Fitting  up  Wash-bottle 10  5 

Solution 11  6 

Evaporation           .......        12  7 

Steam  Bath       .        .        .        .        .        ...        13  8 

Crystallisation              • 14  8 

Precipitation .        15  8 

Filtration 16,  17  9 

Washing  Precipitates 18-21  9 

Drying  Precipitates 22  10 

Ignition .        23  11 

Fusion 24  11 

Sublimation 2S  " 

Flame  Colorations •      . 26  u 

Borax  Bead 27  12 

Use  of  Test-papers 28  12 


Vi  PRACTICAL  AGRICULTURAL  CHEMISTRY 

SECTION    II 
THE   CONSTITUENTS  OF  AIR  AND    WATER 

PARA-  PAGE 
GRAPH 

Air                    29  33 

Oxygen         .                3°-34  *3 

Nitrogen 35"  3§  J5 

Carbon  Dioxide 39-42  16 

Ammonia 43-4^.  18 

The  Atmosphere 47-49  l9 

Water 50  20 

Hydrogen,  Preparation  and  Properties        .      51-55  20 

Water,  Experiments  on                                 .    »      56-60  22 


SECTION    III 

EXPERIMENTS  ON  SOILS,  MANURES, 
FEEDING  MATERIALS,  AND  DAIRY 
PRODUCE 

Soils                    61-67  26 

Manure            68  28 

Manures,  Lime 69-75  28 

Manures,  Potash 76  31 

Manures,  Phosphatic 77-83  31 

Manures,  Nitrogenous 84-87  33 

The  Mixing  of  Manures 88-90  35 

Testing  Manures 91-98  36 

Compound  Manures 99-106  38 

Oil-Cakes 107-117  41 

Grass  and  Hay  . 118  123  44 

Roots 124-129  46 

Cereals 130-132  48 

Milk        .        .        . i33-*39  49 

Butter 140-142  51 

Cheese 143.  »44  5* 


CONTENTS  vii 


SECTION    IV 


QUALITATIVE    ANALYSIS    OF  SOILS 
AND    MANURES 

PARA-  PACE 
GRAPH 

Introductory  Remarks 145-148  53 

General  Rules  for  Working      .        .        .    .  149-157  54 

REACTIONS    FOR    THE   METALS 

Aluminium 158-160  55 

Iron 161-172  56 

Manganese 173-177  57 

Calcium 178-181  58 

Magnesium 182-185  59 

Sodium 186-187  59 

Potassium 188-190  60 

Ammonium 191-193  60 

REACTIONS  FOR    THE   ACID-RADICALS 

Sulphate 194  61 

Carbonate 195  61 

Nitrite 196,  197  61 

Nitrate 198-200  62 

Chloride .        .  201-203  62 

Phosphate 204-207  63 

Silicate 208-210  63 

Organic  Carbon 211,212  64 

Organic  Nitrogen 213,214  64 

Organic  Chlorine 215  64 

Organic  Sulphur 216  65 

TABLES  FOR    QUALITATIVE  ANALYSIS 

Table  I. — Preliminary  Examination  of  Solids 

for  Metals 217-223  65 

Organic  Matter 224-227  66 


Vlll        PRACTICAL  AGRICULTURAL  CHEMISTRY 
Wet  Examination  for  the  Metals 

PARA-  PAGS 
GRAPH 

Solution  of  Solids 228,  229  67 

Notes  to  Table  II 230-235  6/ 

Table  II.— The  Separation  of  the  Metals  .          236  68 

Table  III.— The  Phosphate  Precipitate    .     .          237  70 

Explanation  of  the  Phosphate  Table  .        .  238,  239a  70 
Table    IV. — Preliminary    Examination    for 

Acid-radicals 240-243  71 

Table   V. — Further   Examination  for  Acid- 
radicals        244-249  71 

Analysis  of  Substances  Insoluble  in  Water 

and  Acids 250-258  72 

Example  of  Entry  of  Analysis  in  Note-book  .          259  74 

SECTION    V 

APPARATUS,    CHEMICALS,    AND 
REAGENTS 

Bench  Apparatus       .        .        .        .        .        .         260  76 

Apparatus  for  Sections  L,  II.,  and  III.    .     .          261  77 

Apparatus  for  General  Use    ....          262  78 

Reagents  and  Chemicals 263  79 

Bench  Reagents 264  79 

Chemicals  for  Sections  I.  and  II.  .  .  .  265  80 
Substances  for  Section  III.  ....  266  81 
Reagents  for  Detection  of  Metals  .  .  .  267  82 
Reagents  for  Detection  of  Acid- radicals  .  268  83 
Solutions  for  the  Reactions  of  the  Metals  269  84 
Solutions  for  the  Reactions  of  the  Acid- 
radicals   270  84 

Table    of    the    Atomic    Weights     of    the 

Elements 271  85 

Thermometry  Scales 272  85 

Weights  and  Measures 273,  274  86 

INDEX     .........  88 


PRACTICAL 
AGRICULTURAL    CHEMISTRY 


SECTION   I 

CHEMICAL  MANIPULATION  AND  APPARATUS 

The  student  whose  time  is  very  limited,  on  wotking  through  the 
experiments  described  in  this  book,  may  omit  those  paragraphs  marked 
with  an  asterisk. 

I.  The  Bunsen  Burner. — Where  gas  can  be  obtained 
the  Bunsen  burner  (fig.  i)will  be  found  the  most  convenient 
lamp  for  heating  purposes.  Before 
use  the  coal-gas  is  mixed  with  air,  and 
when  ignited  burns  with  a  feebly 
luminous  flame,  which  deposits  no  soot 
when  a  solid  object  is  held  in  the 
flame.  For  this  reason  the  Bunsen 
or  some  other  atmospheric  burner  is 
nearly  always  employed  for  chemical 
work  in  place  of  the  luminous  flame- 
burner.  The  Bunsen  burner  (fig.  i) 
consists  essentially  of  a  gas-jet  (#), 
which  is  surrounded  by  an  outer  tube 
(c),  in  which  the  air  passing  through 
two  inlets  (b)  mixes  with  the  gas. 
The  mixture  of  air  and  gas  is  burnt  at  the  top  of  the 
outer  tube  (c).  Over  the  air-holes  fits  a  ring,  which  by 
turning  round  will  cut  off  either  wholly  or  partially  the  supply 
of  air.    When  the  flame  is  turned  down  it  is  necessary  to  re- 

B 


Fig.  i 


'I  ^::'./EKAar}CAvL':  AGRICULTURAL  CHEMISTRY      [2-3 

duce  the  supply  of  air,  or  the  gas  will  take  fire  below,  which 
then  gives  off  unpleasant-smelling  products,  and  may  melt 
the  rubber  tubing  attached  to  the  burner.  If  the  burner 
should  thus  take  fire  below,  at  once  turn  off  the  gas,  reduce 
the  air  supply  by  turning  the  ring,  and  relight. 

For  heating  a  large  surface  a  *  rose-top '  may  be  used. 
It  consists  of  a  metal  cap  perforated  with  holes  to  distribute 
the  gas.  The  cap  is  slipped  on  to  the  top  of  the  burner 
when  it  is  required  for  use. 

2.  The  Spirit-lamp. — Where  gas  is  not  available  the 
spirit-lamp  (fig.  2)  forms  a  convenient  heating-lamp.      Like 

the  Bunsen  burner  the  flame  is  non- 
luminous,  and  does  not  smoke;  but  the 
temperature  is  not  so  high,  and  the 
flame  cannot  be  so  conveniently  regu- 
lated. It  consists  of  a  reservoir  con- 
taining methylated  spirit,  into  the  neck 
of  which  passes  a  wick-holder  which 
supports  the  cotton-wick.  When  not 
in  use  the  spirit-lamp  should  be  covered 

with  the  ground-glass  cap  (a)  to  prevent  evaporation  of  the 

spirit. 

Special  forms  of  spirit- lamps,  known  as  '  spirit-bunsens,'  can 

now  be  purchased.     They  burn  a  mixture  of  spirit-vapour  and  air,  and 

give  a  much  higher  temperature  than  does  the  ordinary  spirit-lamp. 

3.  The  Blowpipe. — The  mouth  blowpipe  shown  in 
fig.  3  is  useful  for  obtaining  a  high  temperature.  On  blowing 
a  stream  of  air  by  means  of  this  apparatus  through  an  ordinary 
luminous  flame  a  small  hot  flame  is  obtained.  In  order  to 
produce  this  effect  turn  off  the  air  supply  in  the  Bunsen 
burner  (fig.  1),  so  as  to  obtain  the  luminous  flame.  Next 
turn  down  the  gas  supply  until  the  flame  is  nearly  two 
inches  in  height.  Now  place  the  jet  of  the  blowpipe  just 
over  the  orifice  of  the  burner  and  blow  a  gentle  current  of 
air  into  the  flame.  The  flame  will  then  lose  its  luminosity 
and  appear  as  a  finely  pointed  tongue  of  flame  (fig.  4).  In 
the  use  of  the  blowpipe  the  student  should  practise  so  as 


4-5] 


THE  BLOWPIPE 


to  produce  a  continuous  blast.  This  is  acquired  by  first 
inflating  the  cheeks  with  air  from  the  lungs,  keeping  them 
inflated  until  the  lungs  are  exhausted  of 
air  ;  then  when  inhaling — i.e.  refilling  the 
lungs — the  air  in  the  cheeks  should  be  ex- 
pelled gradually,  and  thus  keep  the  blast 
continuous.  After  a  little  practice  the  stu- 
dent will  be  able  to  breathe  through  the 
nose  during  blowpipe-work,  whilst  he  is 
employing  his  cheeks  and  lungs  to  keep  up 
a  steady  blast. 

4.  For  heating  large  vessels  to  a  high 
temperature  the  table  blowpipe  is  usually 
used.  In  this  blowpipe  the  air  is  forced 
through  the  flame  by  means  of  a.  foot-bellows. 
Since  both  hands  are  at  liberty  it  is  usually 
used  in  glass -working  (paragraphs  5,  6, 
and  7). 

5.  Cutting  and  Bending  Glass  Tube  and 
Rod. — Glass  tube  (or  rod)  may  readily  be  cut  by  first 
making  a  deep  cut  with  a  sharp  triangular  file,  then  holding 
the  tube  on  either  side  of  the  cut,  and  finally  applying  a 


Fig.  3 


strain  partly  between  a  pull  and  a  break.  The  rough  edges 
should  either  be  filed  or  held  for  a  short  time  in  the  Bunsen 
burner,  so  as  to  fuse  the  edges,  and  thus  prevent  the  jagged 
edges  from  cutting  the  hands. 

Glass  tube  (or  rod)  is  readily  bent  by  holding  the  tube 
in  the  upper  part  of  a  fish-tail  burner  (fig.  5),  constantly 

a  2 


4         PRACTICAL  AGRICULTURAL  CHEMISTRY        [6-7 

rotating  the  tube  so  as  to  heat  it  uniformly.    When  the 
glass  becomes  soft  it  may  be  bent  at  any  desired  angle. 


Fig.  s 

When  cold  the  soot  may  be  wiped  off  with  a  duster.  If 
bent  as  described  the  bend  will  be  rounded  and  of  uniform 
bore  throughout.  If  bent  in  a  Bunsen  flame  the  tube  is 
usually  flattened  out  at  the  bend  and  very  liable  to  break. 

6.  Making  Closed  Tubes.— Select  a  piece  of  glass 
tube  about  6  in.  long  and  -^  in.  internal  diameter.  Heat 
it  in  the  middle  portion  by  means  of  the  blowpipe  flame. 
When  quite  soft  draw  it  out,  as  shown,  fig.  6.  Next  heat 
the  portion  (a)  in  the  tip  of  the  flame,  so  that  on  drawing 


Fig.  6 


a 


Fig.  7 

out  again  a  tube  closed  at  one  end  (fig.  7)  is  formed.  The 
closed  end  of  the  tube  may  then  be  rounded  by  heating  it 
strongly  and  blowing  gently  into  the  open  end,  so  as  to 
slightly  expand  the  softened  portion.  Or,  if  required,  a 
bulb  may  be  formed  by  again  heating  the  closed  end  and 
blowing  into  the  tube  more  strongly. 

7.  Mounting  Platinum  Wire.— For  a  number  of 
purposes  (paragraphs  26  and  27)  a  piece  of  platinum  wire, 
about  two  inches  long,  and  fused  into  a  piece  of  glass  tube 
to  act  as  a  holder,  will  be  required.    Draw  out  a  piece  of  glass 


10] 


GLASS  MANIPULATION 


5 


tube,  as  described  above,  break  off  the  tube  at  a  (fig.  6), 
place  one  end  of  the  wire  in  the  thin  tube  so  left,  and  heat 
until  the  glass  fuses  round  the  end  of  the  wire.     Allow  to 


cr 


Fig.  8 


cool.  The  glass  tube  will  form  a  convenient  handle  for 
holding  the  wire  during  heating.  Bend  the  free  end  of  the 
wire  into  a  loop,  when  it  will  be  ready  for  use  (fig.  8). 

8.  Boring  Corks. — Corks  are  readily  bored  by  means 
of  sharpened  brass  tubes.  Select  a  borer  slightly  less  in  dia- 
meter than  the  size  of  the  glass  tube  to  be  inserted.  Press 
the  Gork  against  a  wooden  surface  and  gently  rotate  the  borer 
until  a  clean  hole  is 
cut  (fig.  9).  To  make 
the  hole  smooth  a 
round  file  should  be 
used,  which  will  also 
increase  the  dia- 
meter of  the  hole. 

9.  In  boring  rub- 
ber corks  a  very  sharp 
borer  should  be  used,  and  the  borer  should  be  moistened 
with  glycerine. 

The  cork  borers  can  readily  be  sharpened  by  a  special 
kind  of  knife  sold  for  the  purpose,  or  they  may  be  filed  in 
the  interior  by  a  round  file,  and  on  the  exterior  by  a  tri- 
angular file. 

10.  Fitting  up  Wash-bottle.— Select  a  thin  18  oz. 
conical  flask  (fig.  10).  Procure  a  good,  sound  cork,  free 
from  flaws  or  cracks,  slightly  larger  than  the  inner  diameter 
of  the  neck.  Soften  the  cork  by  rolling  it  backwards  and 
forwards  under  the  sole  of  the  foot  on  the  floor :  this  will 
somewhat  lessen  the  diameter  of  the  cork  and  ensure  a 
good  fit. 


Fig.  9 


PRACTICAL  AGRICULTURAL  CHEMISTRY     [10-11 


Bore  two  holes  through  the  cork,  as  described  in  para- 
graph 8.  Next  bend  a  piece  of  glass  tube  at  an  angle  of 
i2o°,  as  shown  in  fig.  10  (6),  taking  care  that  the  ends  of  the 
tube  are  rounded  (paragraph  5).  Force  one  end  just 
through  the  cork.  Now  bend  another  piece  of  glass  tube 
at  an  angle  of  6o°  (a)  and  pass  it  through  the  second  hole 
in  the  cork,  so  as  to  nearly  touch  the  bottom  of  the  flask. 
If  the  tubes  have  been  carefully  adjusted  they  will  fit 
tightly  into  the  cork,  so  that  when  the  cork  is  placed  in  the 
neck  of  the  flask,  and  one  tube  is  closed  with  the  finger,  no 
<^  air  should  escape  when  air  is  blown 
into  the  flask  from  the  mouth  by 
means  of  the  other  tube. 

Upon  the  end  of  the  larger 
tube  (a)  a  small  piece  of  rubber 
tubing  is  placed,  into  which  is  pushed 
a  short  piece  of  glass  tube  drawn 
out  into  a  jet  (c). 

Now  fill  the  flask  with  distilled 
water.  It  may  either  be  used  for 
propelling  a  fine  jet  of  water  through 
the  jet  (c)  by  blowing  into  the  larger 
tube  (b),  or  a  larger  stream  may  be 
obtained  by  inverting  the  bottle  and  pouring  out  of  the 
tube  (6).  If  hot  water  is  required  the  flask  may  be  placed 
on  wire  gauze  on  a  tripod  stand,  and  the  contents  of  the  flask 
heated  over  the  Bunsen  flame. 

A  rubber  cork  may  be  substituted  for  the  wooden  one, 
and  will  be  found  to  last  much  longer. 

II.  Solution. — Most  solid  substances  dissolve  in  some 
kind  of  liquid.  Water  is  the  most  common  solvent.  The 
amour,  t  dissolved  varies  according  to  circumstances  ;  hence 
some  substances  are  very  soluble,  others  less  so,  and  some 
only  slightly  soluble. 

Solution   usually  takes  place   most  rapidly  when   the 


Fig.  10 


11--12] 


SOLUTION   AND  EVAPORATION 


substance  is  in  a  fine  powder.  Heating  and  shaking  also 
promote  solution. 

Solution  may  be  of  two  kinds  :  (i)  simple,  when  the 
body  dissolved  does  not  change  in  its  chemical  composition, 
and  is  therefore  left  behind  on  evaporating  off  the  liquid  ; 
(2)  chemical,  when  a  body  of  different  composition  is  left 
on  evaporating  off  the  liquid. 

a.  Simple  Solution. — Place  a  little  alum  in  a  3-in. 
evaporating- dish,  nearly  fill  the  dish  with  water.  Heat  over 
the  Bunsen  burner  until  the  solid  dissolves.  Reserve  the 
solution  for  future  use. 


Fig.  11 

b.  Chemical  Solution.— Place  a  few  pieces  of  marble  in 
a  test-tube,  add  a  little  dilute  hydrochloric  acid  (HC1). 
The  marble,  which  is  insoluble  in  water,  will  gradually 
dissolve,  carbon  dioxide  gas  being  given  off  (paragraph  39). 

12.  Evaporation. — On  heating  a  solution  of  a  sub- 
stance the  liquid  portion  is  driven  off—  evaporated—  the  solid 
being  left  behind. 

Experiment— Heat  the  liquid  from  paragraph  1 1  b,  in 
a  small  evaporating  dish  until  the  liquid  is  all  expelled  ; 
white  solid  calcium  chloride  6CaCl2)  will  be  left  behind. 


8        PRACTICAL  AGRICULTURAL  CHEMISTRY      [13—15 

Care  must  be  taken  that  the  flame  is  lessened,  as  the 
liquid  in  the  dish  becomes  reduced,  or  the  liquid  will  spirt, 
i.e.  jump  out  of  the  dish. 

13.  A  very  convenient  form  of  apparatus  is  the  steam- 
bath  shown  in  fig.  11.  It  consists  of  a  copper  bath,  on  the 
upper  side  of  which  are  cut  a  number  of  holes  to  fit  various- 
sized  evaporating-dishes.  The  bath  is  three  parts  filled 
with  water,  and  heated  until  the  water  just  boils.  The 
dishes  containing  the  liquids  to  be  evaporated  can  thus 
be  kept  at  a  temperature  of  nearly  ioo°  C,  and  loss  of  the 
liquid  by  spirting  is  avoided.  The  water  which  is  driven  off 
from  the  bath  when  in  use  should  be  replaced  from  time 
to  time,  so  as  to  keep  the  level  of  the  water  constant,  or  better 
a  bath  may  be  used  which  is  fitted  with  an  arrangement 
for  maintaining  the  water  at  a  constant  level.     See  fig.  14. 


Fig.  12 

14.  Crystallisation. — Take  the  solution  (paragraph 
ii a)  and  heat  over  the  Bunsen  flame  until  about  one-quarter 
of  the  liquid  is  left,  allow  to  cool,  when  crystals  of  alum 
will  form.  If  the  solution  is  too  dilute,  and  no  crystals 
form,  further  evaporation  will  be  requisite.  Most  salts  are 
more  soluble  in  hot  than  in  cold  water;  hence  the  salt 
usually  crystallises  out  on  cooling. 

15.  Precipitation. — Two  clear  solutions  when  added 
together  frequently  give  rise  to  an  insoluble  solid,  which 
gives  a  turbid  appearance  to  the  mixture.  A  body  so  formed 
is  termed  a  precipitate. 

Experiment. — To  a  little  calcium  chloride  solution  in  a 
test-tube  add  a    little  ammonium  carbonate  solution ;   a 


1G-19]         PRECIPITATION    AND   FILTRATION  9 

white   precipitate   of   calcium   carbonate   will   be   formed. 
Reserve  the  test-tube  and  contents  for  use  in  paragraph  1 7. 

16.  Filtration. — Very  often  it  is  necessary  to  separate 
a  solid  from  a  liquid  in  which  it  is  suspended.  This 
operation  is  performed  by  filtration  or  decantation  (para- 
graph 19).  In  the  former  case  the  liquid  and  solid  are 
thrown  upon  porous  paper,  the  liquid  passes  through  the 
paper,  the  solid  being  retained.  Unsized  paper,  known  as 
filter-paper,  is  used  for  this  purpose.  It  is  usually  supplied 
cut  into  circular  pieces. 

17.  Fit  a  filter-paper 
into  a  funnel  (fig.  13)  by 
folding  it  across  twice  at 
right  angles  (fig.  12),  so  as 
to  form  a  conical  bag  as 
shown  at  3.  Press  this 
bag  into  the  dry  funnel, 
and  then  moisten  the  paper 
with  distilled  water.  The 
precipitate  and  liquid  from 
paragraph  15  may  then  be 
poured  into  the  funnel, 
when  the  liquid  passing  iaa^™"  FlG  n 
through  will  be  quite  clear, 
the  solid  remaining  on  the  filter-paper. 

18.  Washing  Precipitates.— Precipitates  may  be 
washed  free  from  adhering  solutions  either  by  decantation  or 
on  the  filter-paper,  or  by  a  combination  of  the  two  processes. 

19.  Washing  by  Decantation.— Prepare  a  little 
more  precipitate,  as  described  in  paragraph  15  j  allow  it  to 
stand  until  the  precipitate  subsides,  then  pour  off  the  clear 
supernatant  liquid.  Add  a  little  distilled  water,  shake  up, 
allow  the  solid  to  again  subside,  and  pour  off  the  clear 
liquid.  Repeat  this  operation  four  or  five  times,  when  all 
the  soluble  matter  will  be  washed  out 


IO      PRACTICAL  AGRICULTURAL  CHEMISTRY     [20-22 

20.  Washing  on  the  Filter-paper. — The  precipi- 
tate on  the  filter-paper  (17)  can  be  readily  washed  by  pouring 
into  the  filter  distilled  water,  allowing  it  to  drain  away,  and 
repeating  the  operation  four  or  five  times.  Hot  water  is 
best  for  this  purpose,  since  it  filters  more  rapidly  than  cold. 
The  stream  of  water  from  the  jet  of  the  wash-bottle  should 
be  used  for  this  purpose. 


21.  In  order  to  ascertain  whether  a  precipitate  is 
thoroughly  washed,  it  is  necessary  either  to  evaporate  a 
few  drops  of  the  water  which-  has  passed  through  the  filter, 
or  to  test  for  some  constituent  present  in  the  liquid  which  is 
to  be  separated.  In  the  present  case,  since  the  liquid  will 
be  alkaline,  the  washing  should  therefore  be  continued 
until  the  wash-water  ceases  to  turn  turmeric  paper  brown 
(paragraph  28). 

22.  Drying  Precipitates. — Precipitates  are  usually 
dried  in  a  steam-oven  (fig.  14),  />.  a  copper  oven  hollow- 


23-26]  IGNITION    AND   SUBLIMATION  II 

cased  so  as  to  contain  water.  The  latter  on  being  boiled 
keeps  the  interior  of  the  oven  approximately  at  a  tempera- 
ture of  too°  C.  The  arrangement  shown  at  (a)  is  for 
maintaining  the  water  at  a  constant  level. 

A  more  rapid  way  of  drying  precipitates  is  to  open  out 
the  filter-paper  containing  the  precipitate  on  a  piece  of  wire 
gauze,  and  hold  it  some  distance  above  the  Bunsen  flame. 

23.  Ignition. — Frequently  substances  require  to  be 
heated  strongly  or  ignited.  This  is  best  performed  in  a 
small  test-tube  called  an  ignition-tube  (6)  or  on  a  piece  of 
platinum  foil  2  in.  x  1  in.,  the  latter  being  held  in  the 
flame  by  means  of  crucible  tongs. 

Experiment. — Heat  a  little  solid  manganese  sulphate  in 
an  ignition-tube  ;  the  substance  will  turn  black,  due  to  the 
production  of  the  oxide. 

24.  Fusion. — On  ignition  some  substances  melt  or 
fuse;  occasionally  other  substances  are  added  before 
fusion. 

Experiment. — Heat  a  mixture  of  sodium  carbonate  and 
potassium  nitrate  with  a  trace  of  manganese  dioxide  on 
platinum  foil ;  a  green  mass  will  be  produced. 

25.  Sublimation. — On  heating,  some  substances  go  off 
in  vapour,  but  condense  again  on  a  cool  surface. 

Experiment. — Heat  a  little  ammonium  chloride  in  an 
ignition-tube  held  in  a  horizontal  position.  The  salt  will 
totally  sublime  and  condense  again  as  a  white  solid  in  the 
cold  part  of  the  tube. 

26.  Flame  Colorations. — Certain  substances  when 
heated  in  a  colourless  flame,  such  as  the  Bunsen  or  blow- 
pipe flame,  give  a  distinct  coloration  to  the  flame. 

Experiment. — Clean  a  piece  of  mounted  platinum  wire 
(7)  by  heating  it  in  the  blowpipe  flame,  moistening  it  with 
hydrochloric  acid,  reheating,  and  repeating  the  operation  if 
necessary.  Take  up  a  little  calcium  chloride  by  means  of 
the  loop  and  hold  in  the  flame.  A  red  coloration  will  be 
given  to  the  flame. 


12     PRACTICAL  AGRICULTURAL  CHEMISTRY     [27-28 

27.  Borax  Bead. — Fuse  a  little  borax  on  the  loop  of  a 
platinum  wire  until  it  becomes  like  a  bead  of  colourless 
transparent  glass.  Now  take  a  very  little  manganese  dioxide, 
and  heat  in  the  outer  blowpipe  flame  ;  a  port-wine  tint  will 
be  imparted  to  the  bead.  Next  heat  in  the  inner  flame ; 
the  bead  will  become  colourless.  It  will  thus  be  seen 
that  the  two  flames  may  give  rise  to  different  coloured 
beads. 

28.  Use  of  Test-papers. — Certain  vegetable  colours 
are  affected  by  the  addition  of  certain  chemicals.  The 
test-papers  in  common  use  are  made  by  soaking  paper  in 
litmus  or  turmeric  solutions.  They  are  usually  purchased 
in  little  books. 

Litmus  occurs  normally  as  a  blue  substance.  Its 
solution  in  water  or  alcohol  is  at  once  turned  red  by  acid 
bodies.  This  reddened  litmus  is  then  sensitive  to  alkalies, 
which  give  the  original  blue  colour  again. 

Turmeric  is  normally  of  a  yellow  colour.  Its  solution 
is  turned  brown  by  alkalies,  the  yellow  colour  being 
restored  by  acids. 

Experiment. — Try  the  effect  of  solutions  of  hydro- 
chloric acid,  sodium  hydrate,  and  sodium  chloride  on 
blue  and  red  litmus  and  turmeric  papers.  It  will  be 
found  the  first  gives  an  acid,  the  second  an  alkaline,  and 
the  third  a  neutral  reaction. 

Thus  by  means  of  test-papers  we  have  a  method  of 
ascertaining  when  a  reagent  is  added  in  excess,  provided 
that  reagent  give  a  different  reaction  to  the  liquid  to  which 
it  is  added. 


29-31] 


13 


SECTION    II 

THE  CONSTITUENTS   OF  AIR  AND    WATER 
AIR 

29.  Air  consists  mainly  of  a  mixture  of  nitrogen  and 
oxygen  gases  :  it  also  contains  small  quantities  of  carbon 
dioxide,  water-vapour,  ammonia  and  nitric  acid. 

Preparation  and  Properties  of  Oxygen 

30.  Place  a  few  crystals  of  potassium  chlorate  in  a  per- 
fectly  dry  test-tube  and  heat  in  the  Bunsen  flame.     The 


Fig.  15 

substance  melts  and  gives  off  bubbles  of  oxygen  gas. 
When  this  takes  place,  introduce  a  glowing  splinter  of  wood 
into  the  mouth  of  the  test-tube.  The  splinter  will  burst 
into  flame.  This  behaviour  of  the  glowing  splinter  is  a  test 
for  the  oxygen  which  is  given  off  from  the  heated  potassium 
chlorate.  The  following  equation  represents  the  chemical 
action  that  takes  place  :  KC103=KCl  +  03. 

31.  In  order  to  investigate  the  properties  of  oxygen  gas 
a  much  larger  quantity  of  the  gas  is  required  than  can  be 
prepared  by  the  above  method. 


14     PRACTICAL  AGRICULTURAL  CHEMISTRY     [32-33 


Choose  a  dry  test-tube  and  fit  a  sound  cork  into  the 
mouth  of  the  tube.  Bore  the  cork,  and  fit  it  with  a 
bent  tube  of  the  shape  shown  in  fig.  15.  Next  powder  in 
a  mortar  about  as  much  potassium  chlorate  as  will  fill  a 
small  watch-glass,  together  with  about  one-fifth  as  much 
manganese  dioxide.  One-third  fill  the  test-tube  with  the 
mixture  and  place  it  in  a  retort-stand,  as  shown  in  the 
figure,  jtfext  place  a  beehive  cell  in  a  larger  vessel  and  add 
water  until  it  reaches  about  one  inch  higher  than  the  top  of 
the  beehive  cell.  Before  commencing  to  heat  the  tube,  fill 
one  of  the  jars  in  which  the  gas  is  to  be  collected  with 
water,  cover  its  mouth  with  a  ground-glass  plate.  Invert  it 
and  place  it  on  the  beehive  cell,  as  shown  in  the  figure, 
removing  the  glass  plate  when  the  mouth  of 
the  jar  is  under  the  water  See  that  the  end 
of  the  delivery-tube  is  directly  beneath  the 
opening  of  the  jar.  Now  heat  the  part  of 
the  oxygen  mixture  (potassium  chlorate  and 
manganese  dioxide)  nearest  the  cork  with  a 
Bunsen  flame.  Oxygen  will  come  off  more 
readily  than  in  the  former  case  (30),  and, 
passing  through  the  delivery-tube,  will  be 
collected  in  the  jar.  As  soon  as  one  jar  is 
filled  with  the  gas,  close  it  with  a  glass  plate 
and  remove  it  from 'the  earthenware  dish,  replacing  it  by 
another  filled  with  water  and  inverted  in  the  same  manner. 
When  three  jars  have  been  filled  in  this  way  remove 
the  delivery-tube  from  the  water  and  discontinue  heating. 

32.  One  of  the  properties  of  oxygen  has  already  been 
shown,  i.e.  its  power  of  rekindling  a  glowing  splinter  of 
wood.  All  substances  which  burn  in  air  burn  still  more 
readily  in  oxygen. 

33.  Burning  Sulphur  in  Oxygen.— Place  a  small 
piece  of  sulphur  on  a  deflagrating  spoon.  Heat  it  in  a 
Bunsen  burner  until  it  ignites,  then  plunge  it  into  a  cylinder 


Fig.  16 


34-36] 


PREPARATION   OF   NITROGEN 


15 


of  the  gas,  as  shown  in  fig.  16.  It  will  burn  brilliantly. 
When  the  sulphur  has  ceased  burning  withdraw  the  de- 
flagrating spoon  and  pour  a  little  water  coloured  with  a  few 
drops  of  blue  litmus  solution  into  the  bottle.  The  sulphur 
dioxide  formed  by  the  combination  of  the  sulphur  with  the 
oxygen  will  be  dissolved,  and  the  litmus  will  be  turned  red, 
showing  that  an  acid  body  has  been  formed. 

34.  Burning  Charcoal  in  Oxygen.— Place  a  piece 
of  charcoal  in  a  clean  spoon  and  burn  it  in  a  jar  of  oxygen, 
just  as  the  sulphur  was  burned  in  the  last  experiment.  It 
will  glow  brightly  but  will  give  no  flame.  After  all  burning 
has  ceased  pour  lime-water  into  the  jar  and  shake  up.  The 
lime-water  will  turn  milky  owing  to  the  presence  of  carbon 
dioxide,  which  is  formed  when  charcoal  is  burned  in 
oxygen.  The  action  of  carbon  dioxide  on  lime-water  is 
the  more  fully  explained  in  paragraph  42. 

Preparation  and  Properties  of  Nitrogen 

35.  The  most  convenient  source  of  nitrogen  is  the  air, 
which  consists  chiefly  of  a  mixture  of  the  two  gases  oxygen 
and  nitrogen  in  the  proportion  of  four  volumes  of  the  latter  to 
one  of  the  former.  To  prepare  nitrogen 
it  is  only  necessary,  then,  to  remove 
the  oxygen  from  a  portion  of  the  air. 

36.  Experiment. — Half  fill  a  stone- 
ware dish  with  water  and  float  on  its 
surface  a  small  evaporating  dish.  In 
the  dish  place  a  piece  of  phosphorus 
about  the  size  of  a  pea.  Care  must 
be  taken  not  to  ignite  the  phosphorus. 
It  should  be  cut  under  water  and  dried  ^Jg 
as  rapidly  as  possible  by  means  of 
filter-paper.  Next  place  a  stoppered 
bell-jar  over  the  basin,  as  shown  in  figure  17.  Ignite  the 
phosphorus  by  touching  it  with  a  hot  wire.    Quickly  withdraw 


16     PRACTICAL  AGRICULTURAL  CHEMISTRY      [37-40 

the  wire  and  stopper  the  bell-jar.  The  interior  will  first  fill 
with  white  fumes,  then  the  phosphorus  will  go  out,  and  finally 
the  white  fumes  will  disappear,  leaving  the  interior  clear 
again.  As  the  fumes  disappear  the  water  will  rise  in  the 
bell-jar,  showing  that  the  volume  of  gas  inside  has  con- 
tracted. 

37.  The  explanation  of  this  is  as  follows  :  As  the 
phosphorus  burns  it  combines  with  the  oxygen  of  the  air  to 
form  phosphorus  pentoxide,  which  is  a  white  solid  body, 
and  hence  appears  as  a  white  cloud.  When  all  the  oxygen 
has  been  used  up  the  phosphorus  goes  out.  Next  the 
phosphorus  pentoxide  dissolves  in  the  water,  and  so 
practically  nothing  is  left  in  the  bell-jar  except  the  nitrogen, 
which  occupies  only  four-fifths  of  the  total  volume  of  the 
oxygen  and  nitrogen  originally  present. 

38.  Experiment. — Nitrogen  neither  burns  nor  does  it 
support  combustion.  To  test  this  add  water  until  the  level 
is  the  same  outside  as  it  is  inside  the  bell-jar,  open  the 
stepper  and  plunge  the  lighted  taper  into  the  gas  ;  the  taper 
will  at  once  be  extinguished. 

Preparation  and  Properties  of  Carbon  Dioxide 

39.  Fit  a  Woulffe's  bottle  with  thistle-funnel  and 
delivery  tube  as  in  fig.  18.  Place  in  the  bottle  a  few 
pieces  of  marble.  Pour  down  the  thistle-funnel  enough 
water  to  cover  the  marble,  then  add  a  little  strong  hydrochloric 
acid.  A  brisk  effervescence  will  take  place,  and  carbon 
dioxide  will  be  evolved. 

40.  Place  a  cylinder  under  the  end  of  the  delivery 
tube.  Since  the  gas  is  so  much  heavier  than  air  it  will 
fall  to  the  bottom.  After  the  apparatus  has  been  work- 
ing for  about  half  a  minute  hold  a  lighted  taper  just  over 
the  mouth  of  the  jar.  When  the  jar  is  full  the  gas  will  come 
in  contact  with  the  taper  and  extinguish  it. 


41-42]         CARBON    DIOXIDE   AND  AMMONIA 


17 


41.  Carbon  dioxide  gas  resembles  nitrogen  in  that  it 
will  extinguish  a  flame  as  shown  in  the  last  experiment,  but 
it  differs  from  it  in  several  ways.  To  show  that  it  is  much 
heavier  than  air  pour  the  gas  from  one  jar  into  another, 
as  shown  in  figure  19.  As  the  gas  is  invisible,  nothing  will 
be  seen  to  pass.  Now  plunge  a  lighted  taper  into  each  of 
the  jars.  In  the  one  which  originally  contained  the  gas, 
the  taper  will  continue  burning,  showing  that  no  carbon 
dioxide  remains,  whilst  in  the  other  jar  the  taper  will  be 
extinguished,  showing  that  the  heavy  gas  has  been  poured 
from  the  first  jar  into  the  second. 

42.  Another  property  by  which  carbon  dioxide  may  be 
recognised  is  its  action  on  lime-water.      Half  fill  a  small 

beaker  with  lime-water 
and  place  it  so  that  the 
delivery-tube  of  the  ap- 
paratus (fig.  18)  dips  into 
the  liquid.  Allow  the  gas 
to  pass  through  the  lime- 
water  for  a  few  minutes. 


I 


Fig.  18 


Fig.  19 


First  the  liquid  becomes  milky,  because  the  lime  has 
combined  with  the  carbon  dioxide  to  form  carbonate  of 
lime  or  chalk,  which  is  not  soluble  in  water.  In  a  short 
time,  however,  the  liquid  becomes  clear  again  :  this  is 
because  the  chalk,  although  insoluble  in  pure  water,  is 
soluble  in  water  which  contains  carbon  dioxide  gas  dissolved 
in  it.     If  the  clear  liquid  is  boiled  for  a  few  minutes  the 

c 


1 8      PRACTICAL  AGRICULTURAL  CHEMISTRY      [43-44 

chalk  will  deposit  as  a  white  incrustation  on  the  sides  and 
bottom  of  the  beaker.  Carbonate  of  lime  exists  in  this 
form  in  natural  waters,  and  is  called  '  temporary  hard- 
ness '  (60  d). 


T — if 


Preparation  and  Properties  of  Ammonia 

43.  Ammonia  is  generally  prepared  by  heating  together 
slaked  lime  and  ammonium  chloride.  Grind  together  in  a- 
mortar  equal  parts  of  ammonium  chloride  and  slaked  lime, 
place  a  little  of  the  mixture  in  a  test-tube  and  heat  it. 
Notice  the  strong  smell  of  the  ammonia  which  is  formed. 

44.  To  obtain  larger  quantities  of  the  gas  it  is  much 
more  convenient  to  prepare  it  from  its  solution  in  water. 
If  strong  ammonia  solution  is  warmed  the  gas  comes  off 

in  a  rapid  stream. 

Set  up  the  apparatus 
shown  in  fig.  20,  placing 
a  small  quantity  of  the 
strongest  ammonia  solu- 
tion in  the  flask.  Since 
ammonia  is  lighter  than 
air  it  may  be  collected 
by  upward  displacement. 
To  do  this  place  a  jar 
over  the  evolution-tube 
and  warm  the  flask  cau- 
tiously. The  gas  will 
ascend  into  the  jar.  Now 
dip  a  glass  rod  into 
FlG-  20  strong   hydrochloric  acid 

and  hold  it  near  the  mouth  of  the  jar.  When  the  jar  is  full 
the  ammonia  gas  coming  in  contact  with  the  hydrochloric 
acid  will  form  dense  white  fumes  around  the  moist  part  of 
the  rod.     Discontinue  heating  and  remove  the  jar. 


45-49]  EXPERIMENTS  ON   AIR  19 

45.  One  of  the  most  striking  properties  of  ammonia  gas 
is  its  extreme  solubility  in  water.  Place  a  ground-glass  plate 
over  the  mouth  of  a  jar  filled  with  the  gas  as  in  the  last 
experiment.  Then  hold  the  jar  so  that  its  mouth  dips  under 
the  surface  of  the  water  contained  in  an  earthenware  dish. 
Remove  the  glass  plate.  The  water  will  rush  up  into  the  jar. 

46.  Another  property  of  ammonia  is  its  action  on  tur- 
meric paper,  which  it  turns  brown.  Take  a  few  drops  of 
strong  ammonia  in  a  test-tube.  Moisten  a  strip  of  turmeric 
paper  and  hold  it  over  the  mouth  of  the  test-tube.  It  will 
probably  become  brown  at  once  from  the  ammonia  which 
escapes  from  the  solution.  If  it  does  not  alter  its  colour 
warm  the  liquid  slightly  ;  the  paper  will  immediately  be- 
come dark  brown. 

EXPERIMENTS   ON  AIR 

47.  Of  the  minor  constituents  of  the  atmosphere  (29) 
carbon  dioxide  and  water-vapour  may  be  readily  detected, 
but  the  presence  of  nitric  acid  and  ammonia  are  less  readily 
shown.  Methods  for  detecting  carbon  dioxide  and  water - 
vapour  in  air  are  described  below. 

48.  Carbon  Dioxide  in  Air.— Pour  a  little  clear 
lime-water  into  a  saucer  or  shallow  evaporating-basin  and 
allow  it  to  stand  for  an  hour.  At  the  end  of  that  time  it 
will  be  covered  by  a  thin  film  of  carbonate  of  lime  or  chalk. 
This  is  produced  by  the  action  of  carbon  dioxide,  as  ex- 
plained in  paragraph  42,  and  shows  the  presence  of  that 
gas  in  the  air. 

49.  Water-vapour  in  Air.— Place  on  a  dry  porce- 
lain tile  a  few  lumps  of  dry  calcium  chloride  and  allow 
them  to  stand  for  an  hour.  At  the  end  of  that  time  the 
lumps  will  have  become  quite  wet.  The  moisture  which 
has  been  thus  attracted  can  only  have  come  from  the  air. 
This   experiment,   therefore,   shows  that  the   air  contains 

water-vapour. 

c  2 


20       PRACTICAL  AGRICULTURAL   CHEMISTRY   [50-51 


WATER 

50.  Water  differs  chemically  from  air  in  being  a  compound 
of  the  two  gases  oxygen  and  hydrogen,  whereas  air  was  seen 
to  be  a  mixture  of  the  gases  nitrogen  and  oxygen. 

The  properties  of  oxygen  have  been  already  described 
(30-34).  The  preparation  and  properties  of  hydrogen  are 
described  below. 

Preparation  and  Properties  of  Hydrogen 

51.  Fit  up  the  apparatus  for  this  experiment  as  shown  in 
fig.  21.     Place  a  handful  of  granulated  zinc  at  the  bottom  of 


Fig.  21 

the  Woulffe's  bottle  and  pour  sufficient  water  down  the  thistle- 
funnel  to  cover  the  zinc.  Now  add  some  strong  hydro- 
chloric acid,  when  a  brisk  effervescence  will  ensue.  Do  not 
collect  the  first  portion  of  gas,  but  after  it  has  been  in  action 
for  two  or  three  minutes  fill  a  test-tube  with  water,  invert  it 
in  the  water,  and  allow  the  gas  to  pass  into  it.  When  it  is 
full  of  gas  close  it  with  your  thumb  and  bring  it  close  to  a 
lighted  burner.  Remove  your  thumb  and  apply  the  light  to 
the  tube.  If  the  gas  be  pure  it  will  burn  steadily ;  if  it  con- 
tain air  it  will   explode  with  a  sharp   squeak.     Continue 


52-55]  PROPERTIES   OF   HYDROGEN  21 

testing  until  it  is  quite  free  from  air,  then   collect  a  few 
cylinders  as  described  in  paragraph  31. 

52.  Hydrogen  burns  but  does  not  support  combustion. 
As  soon  as  a  cylinder  is  full  of  hydrogen  remove  it  from 
the  trough,  keeping  its  open  end  downwards,  and  thrust  a 
lighted  taper  into  it.  The  taper  will  be  extinguished,  but 
the  hydrogen  itself  will  burn  with  a  flame  which  is  scarcely 
visible. 

53.  Hydrogen  is  the  lightest  substance  known.  Fill 
another  cylinder  with  hydrogen  and  pour  the  gas  upwards 
into  a  cylinder  which  contains  nothing  but  air.  Then  test 
each  cylinder  with  a  lighted  taper.  The  one  which  formerly 
contained  the  gas  will  have  no  effect  on  the  taper,  whilst 
the  one  which  formerly  contained  no  hydrogen  will  give  a 
sharp  explosion,  showing  that  hydrogen  is  lighter  than 
air. 

54.  Fill  a  short  thick  cylinder  with  water,  then  invert  it 
in  a  dish  of  water.  Displace  about  two-thirds  of  the  water 
with  hydrogen  and  the  rest  with  oxygen.  Allow  the  gases 
to  stand  for  a  few  minutes  to  mix  thoroughly,  then  apply  a 
lighted  taper ;  a  loud  explosion  will  take  place,  due  to  the 
gases  combining  to  form  water. 

55.  The  energy  of  the  combination  of  the  gases  in  the 
last  experiment  prevents  the  water  formed  from  being  readily 
collected.  But  if  hydrogen  is  allowed  to  combine  with  the 
oxygen  of  the  air  under  suitable  conditions  the  water  may 
be  collected.  Replace  the  bent  delivery-tube  (fig.  21)  by 
a  straight  piece  of  glass  tube  6  inches  long.  Allow  an 
energetic  stream  of  hydrogen  to  pass  for  some  minutes, 
then  ascertain  that  the  hydrogen  is  free  from  air  by  the 
following  test.  Hold  a  small  test-tube  over  the  end  of  the 
upright  tube  for  half  a  minute,  close  the  mouth  of  the  tube 
with  the  thumb  and  apply  a  light.  If  the  gas  is  free  from 
air  it  will  burn  quietly  up  the  tube  j  if  it  explodes  with  a 
squeaking  noise  continue  the  evolution  of  the  gas  until  the 


22      PRACTICAL  AGRICULTURAL  CHEMISTRY      [-56-57 

tube  of  gas  burns  quietly.     To  prevent  accidents  it  is  better 
to  cover  the  Woulffe's  bottle  with  a  glass-cloth. 

When  the  hydrogen  is  free  from  air  ignite  the  stream  of 
gas  and  hold  over  the  flame  a  clean,  dry  beaker.  After  a 
time  drops  of  water  will  collect  inside  the  beaker,  which 
will  be  found  to  have  the  ordinary  properties  of  pure  water. 

EXPERIMENTS  ON  WATER 

56.  Natural  Waters. — Dissolved  substances  are 
always  present  in  the  water  which  occurs  in  nature.  Even 
carefully  collected  rain-water  contains  some  impurities  dis- 
solved out  of  the  air.  Spring,  river,  and  well  waters  con- 
tain also  dissolved  matters,  obtained  from  the  soil  or  rock 
with  which  they  have  been  in  contact. 

57.  Distillation  of  Water.— The  water  obtained 
from  the  general  supply  of  a  town  is  seldom  sufficiently 


Fig.  22 

pure  for  use  in  a  laboratory,  as  it  contains  several  substances 
in  solution.  It  may  be  freed  from  these  impurities  by  the 
process  known  as  distillation.  The  apparatus  required  for 
this  operation  is  shown  in  fig.  22,  and  consists  of  a  retort 
whose  neck  leads  into  a  flask  which  is  kept  as  cool  as 
possible  by  being  immersed  in  a  vessel  of  water.  Half  fill 
the  retort  with  water  and  heat  it  with  a  Bunsen  flame,  prefer- 


58-00]  EXPERIMENTS   ON   WATER  23 

ably  with  the  flame  from  a  rose  burner.  The  water  will  boil, 
and  the  steam  will  pass  over  until  it  comes  into  the  cool  flask, 
where  it  will  condense.  In  this  manner  pure  water  will  be 
collected  in  the  flask,  whilst  the  impurities  are  left  behind 
in  the  retort. 

58.  For  the  tests  described  in  the  next  seven  experiments 
three  kinds  of  water  should  be  used,  i.e.  distilled  water, 
ordinary  water  as  supplied  to  the  laboratory,  and  some 
sample  of  really  impure  water,  such  as  drainage  water. 

59.  Solid  Matter  in  Water.— Half  fill  three  evapo- 
rating-basins  with  the  different  waters  under  consideration 
and  evaporate  each  to  dryness.  Notice  the  residue,  if  any, 
left  in  each  case.  When  the  residue  is  quite  dry  hold  the 
dish  in  a  Bunsen  flame  for  a  minute  or  so.  Should  there 
be  any  organic  impurities  in  the  water,  such  as  are  derived 
from  decomposing  animal  or  vegetable  matter,  the  residue 
in  the  dish  will  become  discoloured  and  blackened.  The 
distilled  water  will  be  found  to  leave  no  residue.  The 
laboratory  water  will  leave  a  residue  which  will  probably 
remain  white  on  further  heating.  The  drainage  water  will 
leave  a  residue  which  blackens  on  heating. 

60.  Various  Dissolved  Salts  in  different  Classes 
of  Water. — The  common  dissolved  impurities  are  the  sul- 
phates and  carbonates  of  lime  and  magnesia,  and  in  smaller 
amounts  common  salt  and  ammonia.  A  few  experiments 
are  described  below  to  show  the  method  of  testing  for  these 
impurities,  and  of  roughly  comparing  the  amounts  present. 

a.  Lime  in  Water. — Half  fill  three  clean  test-tubes 
with  the  three  samples  of  water.  Place  them  side  by  side 
in  the  test-tube  rack  and  add  to  each  a  few  drops  of  am- 
monia and  a  little  ammonium  oxalate  solution  ;  allow  to 
stand  a  few  minutes.  The  distilled  water  will  suffer  no 
change,  whilst  the  other  two  will  become  cloudy.  Notice 
which  gives  the  thickest  cloud,  as  that  one  will  contain 
most  lime,  and  will  probably  be  the  hardest  water. 


24         PRACTICAL  AGRICULTURAL   CHEMISTRY         [60 

b.  Sulphates  in  Water.— It  is  very  seldom  that  a 
natural  water  contains  sulphuric  acid  in  the  free  state,  but 
most  spring  waters  contain  it  in  combination  with  lime  or 
magnesia.  Add  to  portions  of  the  different  kinds  of  water 
in  three  test-tubes  a  drop  of  hydrochloric  acid  and  ten  drops 
of  barium  chloride.  A  cloudiness,  which  may  require  a  few 
minutes  to  form,  shows  presence  of  sulphuric  acid.  The  dis- 
tilled water  contains  no  sulphate,  whilst  the  other  two  con- 
tain it  in  varying  quantities,  as  shown  by  the  milkiness. 

c.  Carbonates  in  Water.— Half  fill  three  small 
beakers  with  specimens  of  the  different  waters  and  boil 
each  for  twenty  minutes.  Pour  out  the  water  and  notice  the 
deposit  (if  any)  in  each  case.  The  deposit  is  due  to  car- 
bonate of  lime,  which  deposits  when  the  carbon  dioxide  is 
driven  out  of  the  water  (42).  If  a  few  drops  of  a  dilute 
hydrochloric  acid  are  added,  the  precipitated  carbonate  will 
effervesce  (195). 

d.  Salt  in  Water.— Half  fill  three  test-tubes  with  the 
samples  of  waters  as  directed  in  the  last  experiment  and 
add  a  drop  of  dilute  nitric  acid  and  ten  drops  of  silver  nitrate 
to  each.  The  distilled  water  will  not  change  in  appearance. 
That  water  which  gives  most  cloudiness  contains  most 
salt. 

e.  Hardness  of  Water.— The  presence  of  dissolved 
salts  of  lime  and  magnesia  in  water  causes  the  precipitation 
of  soap.  Water  which  produces  this  result  is  termed  '  hard/ 
Salt  (sodium  chloride)  if  present  in  large  amount  will  also 
produce  this  result. 

Dissolve  a  shaving  of  soap  in  a  little  distilled  water  and 
shake  up  a  little  of  the  solution  with  the  three  samples  of 
water  previously  placed  in  test-tubes.  The  distilled  water 
will  immediately  produce  a  lather  and  remain  clear,  whereas 
the  other  samples  will  become  turbid  and  produce  no 
lather  until  a  larger  quantity  of  soap  solution  is  added. 
The  amount  of  soap  solution  necessary  to  form  a  lather  is 


60]  EXPERIMENTS   ON    WATER  2$ 

a   rough  indication  of  the   *  hardness '  or  soap-destroying 
power  of  the  water. 

f.  Ammonia  in  Water. — Take  three  test-tubes  half 
filled  with  the  different  kinds  of  water  as  before,  and  to  each 
add  ten  drops  of  Nessler's  Solution.  This  is  one  of  the  most 
delicate  tests  known  to  chemists,  and  should  the  smallest 
trace  of  ammonia  be  present,  the  water  to  which  the  Ness- 
ler's Solution  (265)  has  been  added  will  become  coloured 
yellow  or  brown,  according  to  the  amount  of  ammonia 
present.  So  delicate  is  the  test  that  distilled  water,  unless 
it  has  been  specially  prepared,  will  contain  sufficient  ammo- 
nia to  show  it.  After  the  test-tubes  have  stood  two  or  three 
minutes  notice  their  colour  by  holding  them  over  a  sheet 
of  white  paper  and  looking  down  through  the  length  of  the 
tube.  The  drainage  water  will  be  much  more  coloured 
than  the  other  two.  As  the  most  probable  source  of  am- 
monia in  a  natural  water  is  decaying  animal  matter  it  will 
be  seen  that  it  is  very  necessary  that  drinking  water  shall 
contain  as  little  of  this  substance  as  possible. 


26      PRACTICAL  AGRICULTURAL  CHEMISTRY      [61-63 


SECTION    III 

EXPERIMENTS  ON  SOILS,   MANURES,   FEEDING 
MATERIALS,   AND  DAIRY  PRODUCE 

EXPERIMENTS  ON  SOILS 

61.  Arable  soils  consist  principally  of  four  substances- 
sand,  clay,  limestone,  and  humus  or  organic  matter — 
and  the  varieties  of  soil  are  named  according  to  the  pro- 
portions in  which  the  above  constituents  are  present.  Thus, 
certain  soils  are  known  as  sandy  soils,  clay  soils,  limestone 
soils,  and  peat  soils.  Besides  these  are  loams,  which 
contain  both  sand  and  clay  in  large  quantities;  marls, 
which  consist  principally  of  limestone  and  clay ;  and  cal- 
careous soils,  in  which  sand  and  limestone  occur  together. 

62.  Separation  of  Sand  and  Clay. — Place  ina3-ia 
evaporating-basin  about  as  much  dried  loam  as  will  cover  a 
penny.  Half  fill  the  basin  with  distilled  water,  and  boil  it  for  a 
few  minutes.  Stir  up  and  pour  out  the  whole  of  the  contents 
into  a  small  beaker.  Allow  the  beaker  to  stand  for  a  few 
minutes,  then  pour  off  the  cloudy  liquid  into  another  beaker, 
leaving  the  sediment  behind.  Now  hold  the  beaker  contain- 
ing the  sediment  over  a  sink  and  allow  water  to  run  into  it 
for  a  few  minutes.  The  fine  particles  of  clay  will  be  washed 
away,  and  very  soon  the  water  will  run  off  quite  clear  The 
residue  in  the  beaker  is  sand. 

63.  Action  of  Lime  on  Clay. — Frequently  imie  is 
added  to  a  clay  soil  to  make  it  more  open  and  sandlike  in 
its  properties.  To  illustrate  this  action  pour  into  two  test- 
tubes  a  little  of  the  clay-water  prepared  in  the  last  experiment. 
To  one  of  these  add  a  thimbleful  of  lime-water  and  allow 


64-66]  EXPERIMENTS   ON   SOILS  2J 

them  to  stand  for  an  hour  or  so.  The  clay  will  scarcely 
have  settled  at  all  in  the  one  to  which  no  lime-water  has 
been  added,  whilst  the  other  will  have  become  almost  clear 
owing  to  the  clay  having  fallen  to  the  bottom  of  the  liquid 
as  though  it  were  fine  sand. 

64.  Limestone  in  Soil. — In  paragraph  39  it  was  shown 
that  when  hydrochloric  acid  is  added  to  marble  (which  is  a 
form  of  limestone)  effervescence  takes  place,  and  carbonic 
acid  gas  is  evolved.  Take  a  small  quantity  of  soil  in  a 
test-tube  and  moisten  it  with  water.  Fill  the  test-tube 
about  half  full  of  dilute  hydrochloric  acid.  If  the  soil 
contains  considerable  quantities  of  limestone  the  effer- 
vescence will  be  seen  at  once.  Should  only  traces  be 
present  the  effervescence  may  be  detected  by  holding  the 
mouth  of  the  test-tube  close  to  the  ear,  when  the  sound 
caused  by  the  gas  coming  off  will  be  distinctly  heard. 

65.  Test  for  Lime. — Lime  is  oxide  of  calcium  ;  for  a 
full  set  of  tests  for  that  metal  see  paragraphs  1 78-1 81. 
It  usually  exists  in  soils  combined  with  carbonic  acid. 
To  test  for  lime  in  a  soil :  boil  the  mixture  of  boil  and 
acid  described  in  paragraph  64  for  a  minute,  then  add 
ammonia  to  it  until  it  is  alkaline,  and  filter.  To  the  clear 
liquid  so  obtained  add  a  little  ammonium  oxalate  and  allow 
the  liquid  to  stand  for  a  few  minutes.  A  white  precipitate  or 
cloudiness  shows  that  the  soil  contained  lime. 

66.  Test  for  Organic  Matter  (Humus).— Place  a 
little  soil  on  a  piece  of  platinum  foil  and  hold  it  with  a  pair 
of  crucible  tongs  just  over  the  top  of  a  Bunsen  flame.  The 
soil  will  first  of  all  darken  in  colour  until  nearly  black,  then 
it  will  become  lighter  again  until  it  is  of  much  the  same  colour 
as  it  was  before  heating.  The  reason  of  these  changes  is  that 
the  organic  matter  (which  always  contains  carbon)  becomes 
charred,  and  the  carbon  so  formed  gives  a  dark  colour  to 
the  substance.  After  a  while  the  carbon  itself  burns,  and 
leaves  the  soil  as  it  was  before  the  experiment,  except  that 
the  organic  matter  has  been  burned  away. 


28      PRACTICAL  AGRICULTURAL  CHEMISTRY     [67-69 

*  67.  The  Nature  of  Humus. — The  organic  matter 
or  humus  in  a  soil  consists  principally  of  certain  acids, 
which,  like  all  other  acids,  combine  with  caustic  potash  to 
form  salts.  The  soil  acids  themselves  are  not  soluble  in 
water,  but  the  compounds  which  they  form  with  caustic  potash 
are  soluble.  To  show  this,  place  a  small  quantity  of  peat  soil 
at  the  bottom  of  a  test-tube  and  fill  the  tube  about  one-third 
full  of  caustic  potash  solution.  Warm  for  a  few  minutes, 
then  fill  up  the  test-tube  with  water,  shake  well,  and 
filter.  The  liquid  which  comes  through  will  be  coloured 
brown  by  the  potash  compounds  in  solution.  Take  a 
little  of  the  solution  in  a  test-tube  and  add  an  excess 
of  dilute  hydrochloric  acid.  The  liquid  will  become  cloudy 
because  the  soil  acids  will  be  again  set  free  from  the 
potash,  and,  as  they  are  not  soluble  in  water,  they  will  form 
a  precipitate. 

EXPERIMENTS  ON   MANURES 

68.  The  most  important  constituents  of  manures  arc 
lime  (CaO),  potash  (K20),  phosphoric  acid  (P205),  and 
nitrogen  (N).  Most  natural  manures,  such  as  farmyard 
manure  and  guano,  contain  all  these  substances.  Artificial 
manures  are  generally  made  by  mixing  substances  which 
contain  one  or  more  of  the  above  constituents  in  a  concen- 
trated form.  The  experiments  described  in  paragraphs  69, 
70  are  to  show  the  properties  of  the  various  simple  manures 
before  mixing. 

Lime  Manures 

69.  Slaking  Lime.— Place  a  lump  of  freshly  prepared 
lime,  about  the  size  of  a  small  nut,  on  a  tile  and  pour  a  few 
drops  of  water  on  to  it.  When  this  water  is  soaked  up,  pour 
a  few  more  drops,  and  continue  this  process  as  long  as  the 
lime  will  continue  to  absorb  it  and  still  remain  dry.  The 
lime  will  shortly  become  hot  and  fall  into  a  fine  powder, 


70-72]  LIME  MANURES  2Q 

showing  that  chemical  action  has  taken  place,  and  the  quick- 
lime has  combined  with  the  water  to  form  slaked  lime. 

70.  Solubility  of  Lime. — Although  limestone  (car- 
bonate of  lime)  is  not  soluble  in  pure  water,  slaked  lime 
(hydrate  of  lime)  is.  Place  a  little  powdered  marble  in  a 
test-tube,  and  in  another  place  a  little  of  the  slaked  lime 
obtained  in  the  last  experiment.  Add  to  each  half  a  test- 
tube  full  of  water  and  shake  up.  Allow  both  to  settle  and 
pour  off  the  clear  liquid  into  two  other  test-tubes.  Filter 
if  necessary.  To  each  of  these  two  clear  liquids  add  a  few 
drops  of  ammonium  oxalate.  The  one  in  which  the  marble 
has  been  shaken  will  remain  clear,  showing  that  none  has 
been  dissolved  ;  whilst  the  other  will  give  a  white  precipitate, 
showing  that  some  of  the  slaked  lime  has  entered  into 
solution.1 

71.  Action  of  Air  on  Lime. — When  lime  is  ex- 
posed to  the  air  it  absorbs  carbonic  acid  and  is  converted 
into  carbonate  of  lime,  which  is  known  as  mild  lime.  Pour 
a  little  lime-water  (a  solution  of  slaked  lime  in  water)  into 
an  evaporating-dish  and  leave  it  exposed  to  the  ah'  for  an 
hour  or  two.  At  the  end  of  that  time  it  will  be  covered 
with  a  thin  scum.  This  is  because  the  lime  in  the  solution 
has  been  turned  into  carbonate  of  lime,  which,  being 
insoluble  in  the  water,  forms  a  scum  over  the  surface. 

72.  Action  of  Lime  on  Acids.— Lime  is  not  only 
useful  as  a  food  for  plants,  but  it  improves  the  soil  in  many 
other  ways.  One  of  these  has  already  been  pointed  out  in 
paragraph  63.  Another  use  of  lime  is  to  add  it  to  *  sour ' 
soils,  or  soils  which  contain  such  quantities  of  acid  that  they 
will  not  grow  good  crops.    To  show  this  action,  one-third  fill 

1  Distilled  water  is  seldom  perfectly  free  from  carbon  dioxide ; 
hence  a  trace  of  the  marble  is  often  dissolved,  giving  a  faint  precipitate 
with  ammonium  oxalate.  When  this  is  the  case  the  student  should 
notice  the  great  difference  between  the  precipitate  obtained  after  using 
lime  and  that  obtained  by  using  marble. 


30      FRACTICAL  AGRICULTURAL  CHEMISTRY     [73-75 

a  test-tube  with  distilled  water,  then  add  a  few  drops  of 
hydrochloric  acid  and  a  few  drops  of  litmus  solution.  The 
acid  will  colour  the  litmus  red.  Now  add  a  few  drops  of 
lime-water  and  shake  up.  If  the  liquid  be  still  red  (i.e.  if 
it  be  still  acid)  add  a  few  more  drops  of  lime-water  and 
shake  up  again.  Continue  doing  so  until  the  colour 
changes  to  blue.  When  this  takes  place  all  the  acid  will 
have  been  neutralised. 

*  73.  Action  of  Lime  on  Salts  of  Iron.— Soluble  salts 
of  iron  are  often  injurious  to  crops.  Lime  has  the  property 
of  rendering  these  salts  insoluble.  Dissolve  a  crystal  of 
ferrous  sulphate  (copperas)  in  half  a  test-tube  of  cold  water. 
Add  a  little  lime-water.  The  iron  in  the  solution  will  be 
rendered  insoluble  and  a  dark-coloured  precipitate  of  fer- 
rous hydrate  will  be  formed. 

74.  Sulphur  in  Gas-lime.— Lime  which  has  been 
used  in  the  purification  of  coal-gas,  called  gas-lime,  is  some- 
times used  as  a  manure  and  insecticide,  but  unless  it  is 
exposed  to  the  action  of  the  air  for  a  considerable  time  it 
acts  as  a  plant  poison,  as  it  contains  calcic  sulphide.  To 
show  the  presence  of  a  sulphide,  place  a  little  gas-lime  in  a 
test-tube  and  add  a  little  dilute  hydrochloric  acid.  Effer- 
vescence takes  place  and  the  calcic  sulphide  is  decomposed, 
forming  sulphuretted  hydrogen,  which  may  be  recognised 
by  its  offensive  smell. 

*  75.  Sulphur  in  Gypsum.— Gypsum  (sulphate  of  lime) 
contains  sulphur,  but  as  a  plant-food.  Treat  a  little  gypsum 
as  in  the  last  experiment.  No  sulphuretted  hydrogen  will 
be  given  off.  Mix  a  little  gypsum  in  a  mortar  with  twice  its 
weight  of  powdered  charcoal.  Place  a  little  of  this  mixture 
on  a  piece  of  platinum-foil  and  heat  over  a  Bunsen  flame 
until  all  the  charcoal  is  burned  off.  Allow  to  cool,  then  place 
the  mass  in  a  test-tube  and  add  a  little  dilute  hydrochloric 
acid.  Sulphuretted  hydrogen  will  now  be  evolved,  showing 
that  sulphur  was  present  in  the  gypsum.     The  action  of  the 


76-78]  PHOSPHATIC   MANURES  3 1 

air  on  gas-lime  is  to  turn  the  calcic  sulphide  (CaS)  to  gypsum 
(CaS04).  The  heating  with  charcoal  brings  about  the 
opposite  effect,  i.e.  reduces  the  gypsum  to  calcic  sulphide. 

Potash  Manure 

76.  Potash  in  Kainit— Kainit  is  the  most  common 
potash  manure.  To  show  that  it  contains  potassium,  place 
a  little  kainit  on  a  watch-glass  and  moisten  it  with  dilute 
hydrochloric  acid.  Test  this  substance  in  the  flame  as 
directed  on  page  n.  The  flame  will  appear  yellow,  due  to 
sodium  present  as  an  impurity.  Now  observe  the  flame 
through  an  indigo  prism  or  a  piece  of  cobalt-blue  glass.  It 
will  appear  crimson.     This  is  a  distinctive  test  for  potash 

(189). 

Phosphatic  Manures 

77.  Phosphoric  Acid. — This  generally  occurs  in 
artificial  manures  as  a  phosphate  of  lime.  These  phosphates 
are  four  in  number,  and  each  has  its  own  distinctive 
properties.  Their  chemical  names  and  formulae  are  as 
follows  : — 

a.  Monocalcic  phosphate  .  CaO.(H20)2.P205 

b.  Bicalcic  phosphate  .  (CaO)2.H2O.P205 

c.  Tricalcic  phosphate  »     (CaO)3.P205 

d.  Tetracalcic  phosphate  (CaO)4.P205 

Their  commercial  names  are — 

a.  Superphosphate  of  lime.  b.  Reverted  phosphate. 

c.  Bone  or  mineral  phosphate,     d.  Slag  phosphate. 

The  properties  of  slag  phosphate  are  very  similar  to 
those  of  reverted  phosphate,  so  in  the  next  three  experi- 
ments reverted  phosphate  is  not  considered,  but  it  is  referred 
to  in  paragraph  81. 

78.  Action  of  Water  on  Phosphates.— Into  three 


32      PRACTICAL  AGRICULTURAL  CHEMISTRY      [79-81 

test-tubes  introduce  equal  quantities  respectively  of  coprolite 
powder  (which  contains  bone  phosphate),  basic  slag  (which 
contains  slag  phosphate),  and  superphosphate.  About  as 
much  as  can  be  held  on  a  sixpence  will  be  sufficient.  Half 
fill  each  test-tube  with  distilled  water  and  shake  up.  Filter 
each  one  into  a  clean  test-tube  through  separate  filters.  If 
the  solutions  do  not  come  through  clear,  pass  them  through 
the  filters  again.  Now  test  each  solution  for  phosphoric 
acid.  This  is  done  by  adding  an  excess  of  ammonium 
molybdate  solution  and  boiling  ;  a  yellow  precipitate 
shows  that  phosphoric  acid  is  present.  It  will  be  found 
that  the  liquid  from  the  superphosphate  contains  phos- 
phoric acid,  but  that  the  others  do  not,  showing  that 
superphosphate  of  lime  is  the  only  one  of  the  three 
substances  that  is  soluble  in  water. 

*  70.  Action  of  Ammonium  Citrate  on  Phos- 
phates.— Place  small  quantities  of  superphosphate,  slag 
and  coprolite  powder  in  separate  test-tubes,  as  in  paragraph 
78.  Shake  up  with  ammonium  citrate  solution.  Filter 
and  test  with  ammonium  molybdate  as  before.  This  time 
the  liquids  from  both  the  slag  and  the  superphosphate  will 
be  found  to  contain  phosphoric  acid,  whilst  that  from  the 
bone  phosphate  will  not,  showing  that  both  superphosphate 
and  slag  phosphate  are  soluble  in  ammonium  citrate,  whilst 
bone  phosphate  is  not. 

80.  Action  of  Dilute  Nitric  Acid  on  Phosphates. 
Proceed  exactly  as  in  the  two  previous  experiments, 
treating  the  different  phosphates  with  dilute  nitric  acid. 
Filter  and  test  as  before.  All  three  phosphates  will  be 
found  to  be  soluble  in  nitric  acid,  and  will  therefore  give 
the  molybdate  test. 

81.  Reversion  of  Superphosphate.— When  a  super- 
phosphate is  placed  on  the  soil  the  rain  dissolves  the  soluble 
substance  and  thoroughly  impregnates  the  soil  with  it.  If 
it  were  to  remain  soluble,  a  quantity  would  eventually  be 


82-84]  NITROGENOUS  MANURES  33 

washed  away  into  the  drains.  This,  however,  does  not 
occur,  as  several  substances  in  the  soil  cause  it  to  '  revert,' 
or  turn  into  reverted  phosphate,  which,  like  slag  phosphate, 
is  insoluble  in  water.  The  principal  substances  which 
bring  about  this  reversion  are  lime,  oxide  of  iron,  and 
alumina.     This  reversion  is  shown  in  the  next  experiment. 

82.  Action  of  Lime  on  Superphosphate. — Mix  a 
little  superphosphate  in  a  mortar  with  twice  its  weight  of 
freshly  slaked  lime.  Grind  them  well  together  and  intro- 
duce a  small  quantity  into  a  test-tube.  Add  distilled  water 
and  shake  well,  then  allow  to  settle.  When  the  liquid  has 
become  n2arly  clear,  filter  and  test  the  clear  liquid  with 
ammonium  molybdate.  No  phosphoric  acid  will  be  found. 
The  lime  has  reverted  the  superphosphate  and  rendered  it 
insoluble. 

*  83.  Action  of  Ammonium  Citrate  on  Reverted 
Phosphate. — Take  a  little  more  of  the  mixture  of  lime 
and  superphosphate  made  in  the  last  experiment  in  a  test- 
tube  and  treat  it  with  ammonium  citrate  solution.  Filter, 
and  test  with  ammonium  molybdate.  The  reverted  phos- 
phate will  be  found  to  resemble  slag  phosphate  in  that  it 
dissolves  in  ammonium  citrate. 

The  vegetable  acids  in  soil  act  very  much  in  the  same 
way  as  ammonium  citrate,  so  that  the  reverted  phosphate, 
which  has  been  formed  and  thoroughly  mixed  with  the  soil 
by  the  action  of  rain,  lime,  &c,  on  superphosphate,  is  slowly 
redissolved  and  given  up  to  the  plants  as  food. 

Nitrogenous  Manures 

84.  The  nitrogen  in  manures  occurs  in  one  or  more  of 
three  forms  known  chemically  as  organic  nitrogen,  ammo- 
niacal  nitrogen,  and  nitric  nitrogen.  In  whatever  form  it 
may  occur,  the  action  of  the  organisms  in  the  soil  is  to  turn 
it  into  the  last  of  the  three,  as  this  is  the  only  form  in  which 

D 


34      PRACTICAL  AGRICULTURAL  CHEMISTRY     [85-87 

it  is  fit  for  plant-food.     The  following  three  experiments 
show  how  the  different  forms  may  be  recognised. 

85.  Test  for  Organic  Nitrogen.— Mix  together  in  a 
mortar  about  as  much  shoddy  (which  has  been  cut  up  very 
finely  with  a  pair  of  scissors)  as  can  be  heaped  up  on  a  shil- 
ling with  about  four  times  its  weight  of  soda  lime.  Heat  a 
little  of  this  mixture  strongly  in  an  ignition-tube  (6).  Am- 
monia gas  will  be  given  off,  which  may  be  recognised  by  its 
smell,  and  also  by  the  fact  that  it  turns  moist  turmeric 
paper  brown. 

Treat  a  little  sulphate  of  ammonia  in  exactly  the  same 
way  as  the  shoddy.  Ammonia  will  be  given  off  more 
readily  than  in  the  former  case. 

Treat  a  little  nitrate  of  soda  in  the  same  way.  No  am- 
monia will  be  given  off. 

Shoddy  contains  organic  nitrogen,  sulphate  of  ammonia 
contains  ammoniacal  nitrogen,  and  nitrate  of  soda  contains 
nitric  nitrogen.  From  the  experiment  just  performed  it  will 
be  seen  that  the  organic  and  ammoniacal  forms  are  similar 
in  that  they  both  give  off  ammonia  when  heated  with  soda 
lime.  They  are  distinguished  from  each  other  by  the 
experiment  described  in  paragraph  86. 

86.  Test  for  Ammoniacal  Nitrogen.— Take  three 
test-tubes  :  in  the  first,  place  a  little  shoddy,  cut  up  fine ; 
in  the  second,  a  little  sulphate  of  ammonia ;  and  in  the 
third,  a  little  nitrate  of  soda.  Half  fill  each  test-tube  with 
potassic  hydrate  solution,  and  boil  each  in  turn.  The  one 
containing  sulphate  of  ammonia  will  give  off  ammonia,  which 
may  be  recognised  as  before,  whilst  the  other  two  will 
not  Ammoniacal  nitrogen  may  always  be  recognised  in 
this  way. 

87.  Test  for  Nitric  Nitrogen. — Take  separate  small 
portions  of  sulphate  of  ammonia,  shoddy,  and  nitrate  of 
soda  in  test-tubes  and  add  water.  Filter  each  and  to  the 
clear  liquid  add  a  few  drops  of  indigo  solution  ;  then  pour 


88-90]  THE  MIXING  OF  MANURES  35 

in  strong  sulphuric  acid  until  the  volume  of  liquid  is 
about  doubled.  In  the  case  of  shoddy  and  sulphate  of 
ammonia  no  change  will  take  place.  With  nitrate  of  soda 
the  indigo  will  be  bleached.  This  operation  may  be  used 
as  a  test  for  nitrates  in  manures. 

The  Mixing  of  Manures 

88.  In  mixing  manures  care  must  be  taken  not  to  mix 
two  substances  which  act  chemically  upon  each  other. 
Attention  has  already  been  called  to  the  fact  that  lime  acts 
upon  superphosphate  (82),  rendering  the  phosphoric  acid 
insoluble  in  water  ;  and  since  basic  slag  contains  a  certain 
quantity  of  lime  it  should  not  be  mixed  with  super- 
phosphate. Other  substances  which  should  not  be  mixed 
are  shown  in  paragraphs  89  and  90. 

89.  Action  of  Superphosphate  on  Nitrate  of 
Soda. — Mix  equal  quantities  of  superphosphate  and 
nitrate  of  soda  in  a  mortar.  Notice  the  peculiar  smell  of 
the  mixture.  Heat  a  small  quantity  in  an  ignition- tube. 
It  will  give  off  brown  fumes.  The  reason  is  that  super- 
phosphate contains  a  certain  amount  of  free  sulphuric  acid 
which  is  used  in  its  manufacture,  and  tlus  acts  upon  the 
nitrate  of  soda,  setting  free  nitric  acid,  which  is  recognised 
by  its  smell  and  the  brown  fumes  formed  when  it  is  heated. 
Now  since  nitric  acid  contains  nitrogen,  and  is  volatile,  it 
will  pass  off  into  the  air,  and  so  nitrogen  will  be  lost. 
Further,  nitric  acid  is  a  very  corrosive  substance,  and  will 
attack  the  bags  in  which  manure  is  stored.  Hence  super- 
phosphate and  nitrate  should  never  be  mixed  before  ap- 
plying them  to  the  land. 

90.  Action  of  Slag  on  Sulphate  of  Ammonia.— 
Mix  a  small  quantity  of  sulphate  of  ammonia  with  about 
six  times  its  bulk  of  basic  slag  in  a  mortar.  Notice  the 
smell  of  ammonia.  Heat  a  little  of  the  mixture  in  an 
ignition-tube,  and  hold  a  piece  of  moist  turmeric-paper  over 

d2 


36      PRACTICAL  AGRICULTURAL  CHEMISTRY     [91-94 

the  end  of  the  tube.  The  paper  will  become  brown.  This 
experiment  teaches  that  when  these  two  substances  are 
mixed  ammonia  passes  off  into  the  air  and  is  lost ;  and 
since  ammonia  contains  nitrogen  this  loss  is  a  serious  one. 


TESTING   MANURES 

91.  To  find  the  exact  value  of  a  manure  it  is  necessary, 
to  make  a  full  quantitative  analysis.  There  are,  however, 
a  few  simple  tests  by  which  the  purity  of  a  manure  or  the 
composition  of  a  mixed  manure  may  be  recognised.  These 
are  detailed  in  paragraphs  92-106. 

92.  Ammonia  in  Guano.— No  single  test  can  be 
applied  which  will  guarantee  the  purity  of  a  Peruvian  guano, 
but  the  one  described  in  this  paragraph,  together  with  those 
in  the  next  two  experiments,  will  give  a  fair  idea  of  its 
genuineness.  Take  a  little  guano  in  a  test-tube,  and  treat  it 
with  potash  exactly  as  was  described  in  the  case  of  nitrogen- 
ous manures  (86).  A  genuine  guano  contains  ammoniacal 
nitrogen,  and  hence  ammonia  will  be  evolved,  which  will 
turn  turmeric-paper  brown. 

93.  The  Ash  of  Guano.— Place  a  little  guano  on 
a  piece  of  platinum  foil,  and  hold  it  by  means  of  a  pair  of 
crucible  tongs  in  the  flame  of  a  Bunsen  burner.  The 
guano  will  first  darken  in  colour,  then  catch  fire  and  flare 
up.  When  it  ceases  burning  a  black  mass  of  charcoal  will 
be  left.  Continue  heating  until  all  the  charcoal  is  burned 
off.  The  mass  now  left  on  the  foil  is  known  as  the  ash  of 
the  guano,  and  should  be  quite  white.  If  it  is  brown  the 
guano  has  been  adulterated. 

94.  Soluble  Phosphoric  Acid  in  Guano. — Treat 
a  small  quantity  of  guano  with  water  in  a  test-tube  as 
described  in  paragraph  78.  Filter  and  heat  the  liquid  with 
excess  of  ammonium  molybdate  solution.  A  yellow  pre- 
cipitate will  be  formed,  showing  that  the  guano  contained 


95-98]  TESTING   MANURES  37 

phosphoric  acid  in  a  soluble  state.  The  guano  may  be 
distinguished  from  superphosphate  by  moistening  a  small 
quantity  on  a  tile  and  laying  a  piece  of  blue  litmus  over  it. 
The  litmus  will  not  change.  If  this  be  tried  with  super- 
phosphate the  litmus-paper  will  be  reddened. 

95.  Volatility  of  Sulphate  of  Ammonia. — Place 
a  few  crystals  of  pure  sulphate  of  ammonia  on  a  piece  of 
platinum  foil,  and  heat  over  a  Bunsen  flame.  The  crystals 
will  first  of  all  melt,  then  white  fumes  will  rise  from  the 
substance,  and  finally  it  will  vanish  entirely,  leaving  no 
trace  whatever  on  the  foil.  -  Repeat  the  experiment  with  a 
few  crystals  of  commercial  sulphate  of  ammonia.  Exactly 
the  same  series  of  changes  will  take  place,  except  that  a 
slight  film  of  impurity  will  be  left  on  the  foil.  The  smaller 
this  film,  the  purer  the  sulphate  will  be. 

06.  Thiocyanates  in  Sulphate  of  Ammonia.— 
Occasionally  sulphate  of  ammonia  contains  a  powerful  plant 
poison,  known  as  thiocyanate  of  ammonia,  which  should 
always  be  tested  for.  Add  to  a  solution  of  ammonium 
thiocyanate  a  few  drops  of  ferric  chloride  solution  ;  a  blood- 
red  liquid  will  be  formed.  Now  make  a  solution  of  com- 
mercial sulphate  of  ammonia  in  water  and  treat  in  the  same 
way  by  adding  a  drop  of  ferric  chloride.  Should  the  least 
red  coloration  occur,  the  sulphate  is  unfit  for  use. 

97.  Action  of  Heat  on  Bones.— Samples  of  bones 
can  usually  be  recognised  by  their  appearance,  except  when 
in  the  state  of  bone-flour.  Bone-flour  may  be  recognised 
by  the  following  test.  Heat  a  little  of  the  substance  on 
platinum  foil  as  in  paragraph  93.  The  bones  will  give  off 
an  offensive  smell,  which  is  easily  recognisable.  The  sub- 
stance will  next  blacken  from  the  formation  of  carbon, 
and  finally  become  quite  white  again,  owing  to  the  organic 
matter  being  burnt  away  and  only  ash  left. 

98.  Action  of  Acid  on  Bones.— Place  a  small 
quantity  of  bone-flour  at  the  bottom  of  a  test-tube  and  add 


38      PRACTICAL  AGRICULTURAL  CHEMISTRY    [99-101 

a  small  quantity  of  dilute  hydrochloric  acid.  The  liquid 
will  effervesce,  owing  to  the  fact  that  bones  contain  carbonate 
of  lime. 

COMPOUND   MANURES' 

*  99.  The  following  set  of  experiments  (paragraphs  100- 
106)  should  be  performed  on  several  mixed  manures.  The 
object  of  the  experiments  is  to  find  out  what  are  the  principal 
constituents  of  the  manures. 

*  100.  Test  for  Acidity.— Place  a  little  of  the  mixed 
manure  on  a  watch-glass,  moisten  it  thoroughly  with  water, 
and  lay  a  piece  of  moist  blue  litmus-paper  upon  it.  Should 
the  litmus-paper  immediately  become  red,  the  manure  con- 
tains some  acid,  and  most  probably  contains  superphosphate 
of  lime. 

*  101.  Test  for  Soluble  Phosphate.— Place  about 
as  much  of  the  manure  as  could  be  held  on  a  penny  in  a 
mortar,  cover  with  cold  distilled  water,  and  grind  into  a  paste 
with  the  pestle.  Allow  the  liquid  to  settle  for  two  or  three 
minutes,  then  filter  it,  washing  the  mud  into  the  filter-paper 
with  hot  water.  Save  the  residue  for  the  next  experiment 
Divide  the  filtrate  into  two  portions  in  test-tubes.  Test  one 
portion  for  phosphoric  acid  by  boiling  with  excess  of  ammo- 
nium molybdate  solution. 

Should  a  yellow  precipitate  occur,  then  the  manure  con- 
tains soluble  phosphoric  acid,  and  should  the  manure  have 
been  proved  by  the  last  experiment  to  be  acid  then  we  may 
consider  that  it  contains  either  superphosphate  or  dissolved 
bones. 

To  the  second  portion  of  the  filtrate  add  ammonia  ;  a 
white  precipitate  of  phosphate  will  be  formed.  Allow  this 
to  settle  and  notice  the  colour  of  the  liquid.  If  it  be  quite 
colourless,  then  the  soluble  phosphate  was  mineral  super- 

1  Two  or  three  mixtures  of  the  more  important  manures  should  be 
provided  and  the  student  allowed  to  discover  their  constituents. 


102-103]  TESTING  MANURES  39 

phosphate ;  if  the  liquid  be  at  all  brown  then  the  soluble 
phosphate  was  most  probably  dissolved  bones.  From  this 
experiment,  therefore,  we  learn  first,  whether  the  manure 
contains  soluble  phosphate,  and  secondly,  whether  that 
phosphate  was  prepared  from  bones  or  from  a  mineral 
phosphate. 

*  102.  Test  for  Insoluble  Phosphate.  — Should 
soluble  phosphate  have  been  found  in  paragraph  ioi,  we  are 
pretty  certain  to  find  insoluble  phosphate  also.  This  is 
tested  for  in  the  substance  saved  on  the  filter-paper  from 
the  last  experiment.  Scrape  the  mud  off  the  filter-paper 
and  place  in  a  3 -inch  evaporating-dish ;  just  cover  the 
substance  with  strong  hydrochloric  acid  and  warm  for  a  few 
minutes.  When  as  much  has  dissolved  as  is  possible  fill 
the  dish  nearly  full  of  distilled  water  and  stir  well.  Filter. 
The  residue  will  be  the  sand  which  was  present  in  the 
manure.  Divide  the  liquid  which  comes  through  into  two 
portions.  Boil  one  portion  with  ammonium  molybdate. 
Should  a  yellow  precipitate  form,  then  insoluble  phosphate 
was  present.  To  the  other  portion  add  ammonia,  and 
notice  the  colour  of  the  precipitate.  If  the  insoluble  phos- 
phate has  been  derived  from  bones  the  precipitate  will  be 
quite  white.  If  it  has  been  derived  from  mineral  phosphate 
the  precipitate  will  probably  contain  phosphate  of  iron,  and 
be  more  or  less  brown.  From  this  experiment  we  learn 
whether  the  manure  contains  insoluble  phosphate,  and,  if  so, 
whether  it  is  made  from  bones  or  mineral. 

*  103.  Test  for  Organic  Nitrogen.— Boil  up  a  small 
quantity  of  the  manure  with  water  in  a  3-inch  evaporating- 
basin.  Filter  and  wash  with  the  spray  from  a  wash- bottle  ; 
keep  the  liquid  for  paragraph  105.  When  the  liquid 
and  washings  have  all  run  through,  take  the  filter  and  its 
contents  out  of  the  funnel  and  place  them  in  a  dry  evapo- 
rating-basin,  and  put  this  to  dry  in  a  steam-oven.  (Whilst 
the  substance  is  drying  proceed  with  the  next  experiment) 


40    PRACTICAL  AGRICULTURAL  CHEMISTRY   [104-106 

When  quite  dry,  remove  the  substance  from  the  filter-paper 
to  a  mortar,  and  there  mix  it  with  about  three  times  its 
weight  of  soda-lime.  Heat  some  of  this  mixture  in  an 
ignition-tube  and  test  the  evolved  gases  with  turmeric-paper. 
A  brown  coloration  given  to  the  paper  indicates  organic 
nitrogen.  The  reason  for  the  preliminary  washing  with 
water  is  to  remove  any  sulphate  of  ammonia  or  other  sub- 
stance which  might  contain  ammoniacal  nitrogen. 

*  104.  Test  for  Ammoniacal  Nitrogen.— Warm  a 
little  of  the  manure  in  a  test-tube  with  caustic-potash 
solution ;  test  the  vapour  which  comes  off  with  turmeric- 
paper  as  directed  in  paragraph  86.  Should  the  paper  turn 
brown,  ammonical  nitrogen  is  present  in  the  manure ;  and 
since  sulphate  of  ammonia  is  the  principal  substance  in 
manures  which  contain  nitrogen  in  this  form,  we  may 
usually  assume  that  the  brown  coloration  indicates  that 
sulphate  of  ammonia  was  present  in  the  manure. 

*  105.  Testfor  Nitric  Nitrogen.— Nitric  nitrogen  is 
generally  added  to  manures  in  the  form  of  nitrate  of  soda, 
but  many  natural  manures  contain  nitrate  of  lime.  This  is 
especially  the  case  with  bat's  guano.  For  this  test  use  the 
clear  liquid  saved  from  paragraph  103.  Follow  out  exactly 
the  test  described  in  paragraph  87.  Should  the  indigo  be 
bleached  the  manure  contains  nitric  nitrogen. 

*  106.  Test  for  Potash. — Heat  a  little  of  the  manure 
on  platinum  foil  in  the  Bunsen  flame  until  all  the  carbo- 
naceous matter  is  burned  off.  Remove  the  ash  which  is  left  to 
a  watch-glass  and  moisten  it  with  hydrochloric  acid.  Test  the 
substance  in  the  flame  on  a  loop  of  platinum  wire,  viewing 
the  colour  through  an  indigo-prism  or  a  piece  of  cobalt-blue 
glass.  Should  the  flame,  when  viewed  thus,  appear  crimson, 
the  manure  contains  potash.  The  most  usual  forms  in 
which  potash  is  added  to  mixed  manures  are  sulphate  of 
potash,  muriate  of  potash,  and  kainit,  which  is  a  double 
sulphate  of  potash  and  magnesia. 


107-109]   EXPERIMENTS   ON    FEEDING   MATERIALS  41 


EXPERIMENTS  ON   FEEDING  MATERIALS 

The  experiments  described  below  show  some  of  the 
properties  of  feeding  materials  ;  they  are  divided  into  four 
sets,  viz.  experiments  on  oil-cakes,  experiments  on  grass, 
experiments  on  turnips,  and  experiments  on  cereal  foods. 

Oil-cakes. 

107.  The  principal  kinds  of  oil -cake  are  linseed  cake 
and  cotton  cake,  but  many  other  substances  are  used, 
such  as  rape,  palm-nut,  and  various  flavouring  materials. 
The  chemical  constituents  which  affect  the  feeding  value  of 
oil-cakes  are  much  the  same,  whatever  the  seed  used. 
The  constituents  are  water,  oil,  albuminoids,  carbohydrates, 
woody  fibre,  and  sand,  the  last  two  forming  the  indigestible 
part  of  the  cake.  The  meaning  of  the  above  chemical  terms 
is  explained  as  far  as  possible  in  the  following  experiments. 

108.  Water  in  Oil-cakes.— Grind  up  a  piece  of  lin- 
seed-cake in  a  mortar  and  place  a  little  of  the  powder  in  a 
bulb-tube  with  a  neck  about  eight  inches  long.  Boil  some 
water  in  a  small  beaker  standing  on  a  wire  gauze.  Now 
hold  the  bulb  containing  the  cake  just  beneath  the  surface 
of  the  boiling  water  in  a  slanting  position,  so  that  the  bulb 
and  cake  may  be  heated  up  to  the  boiling-point  of  water, 
whilst  the  rest  of  the  tube  is  kept  cool.  In  a  very  short 
time  water-vapour  will  come  off  from  the  apparently  dry 
cake  and  condense  in  the  cooler  part  of  the  tube,  where  it 
may  be  seen  to  dim  the  inner  surface  of  the  glass  tube. 

109.  Oil  in  Oil-cakes. — Spread  out  a  little  linseed- 
cake,  which  has  been  ground  up  in  a  mortar,  on  a  piece  of 
filter-paper.  Lay  the  paper  on  a  clean  white  tile  and  just 
moisten  the  cake  with  ether.  After  it  has  stood  for  a  minute 
exposed  to  the  air,  the  greater  part  of  the  ether  will  have 
evaporated.     Place  the  paper  for  five  minutes  in  the  steam- 


42    PRACTICAL  AGRICULTURAL  CHEMISTRY  [l  10-111 

oven  ;  after  this  time  brush  the  dry  linseed-powder  from  its 
surface.  Grease-marks  will  be  found  on  the  paper,  showing 
that  the  cake  contained  oil.  This  oil  not  only  helps  in 
forming  the  fat  of  the  animal  feeding  on  it,  but  it  also  helps 
in  the  development  of  animal  heat. 

1 10.  Albuminoids  in  Oil-cakes. — Albuminoids  are 
essentially  the  flesh-forming  compounds  in  the  cake,  and 
they  are  distinguished  from  other  constituents  by  the  fact 
that  they  contain  nitrogen.  Mix  a  little  powdered  linseed- 
cake  with  soda-lime  and  heat  some  of  the  mixture  in  an 
ignition-tube.  Ammonia  will  be  given  off,  and  may  be  tested 
for  with  moist  yellow  turmeric-paper  as  described  in  para- 
graph 85.  This  ammonia  is  formed  by  the  action  of  soda- 
lime  on  the  nitrogen  of  the  albuminoids. 

*  in.  Carbohydrates  in  Oil-cakes.  —  The  name 
'carbohydrate'  is  given  to  a  large  class  of  bodies  containing 
the  three  elements,  carbon,  hydrogen,  and  oxygen.  Starch, 
sugar,  and  dextrin  are  examples  of  carbohydrates.  Most  of 
these  bodies,  on  being  heated  for  some  time  with  dilute  sul- 
phuric acid,  are  converted  into  grape-sugar.  Half  fill  an 
evaporating-basin  with  dilute  sulphuric  acid  (the  ordinary 
dilute  acid  used  in  the  laboratory  must  be  mixed  with  twice 
its  volume  of  water  for  this  experiment).  Throw  on  to  the 
surface  of  the  acid  liquid  at  much  powdered  linseed-cake  as 
can  be  held  on  a  penny.  Boil  gently  over  a  Bunsen  flame, 
supporting  the  basin  on  a  tripod  and  pipeclay  triangle.  Add 
a  little  hot  water  from  time  to  time  as  the  liquid  evaporates, 
to  prevent  the  acid  becoming  too  strong.  When  it  has  boiled 
for  five  minutes  remove  from  the  flame,  allow  to  cool,  and 
filter.  Grape-sugar  must  now  be  tested  for  in  the  clear 
solution.  This  is  done  by  adding  potash  to  the  acid  solution 
until  it  is  slightly  alkaline,  then  a  few  drops  of  Fehling's 
Solution  (266),  and  heating.  The  blue  colour  of  the 
Fehling's  Solution  will  be  destroyed,  and  a  light-red  or  yellow 
precipitate  of  cuprous  oxide  will  be  formed. 


H2-115]  OIL-CAKES  43 

*  112.  Woody  Fibre  in  Oil-cakes.— The  woody 
fibre  and  the  sand  are  the  indigestible  portions  of  oil-cakes. 
Woody  fibre  may  be  shown  to  be  present  in  oil-cake  in  the 
following  way. 

Take  as  much  ground  linseed-cake  as  can  be  held  on  a 
sixpence,  place  in  a  test-tube,  and  fill  the  test-tube  about  one- 
third  full  of  glycerine.  Now  heat  very  cautiously  in  the 
Bunsen  flame  until  the  glycerine  just  boils.  Keep  it  hot 
for  about  a  minute,  then  allow  it  to  cool.  Nearly  fill 
the  test-tube  with  water,  warm  again,  and  filter.  The  sub- 
stance left  on  the  filter  will  be  nearly  pure  woody  fibre. 

*  113.  Sand  in  Oil-cake. — Burn  a  little  oil-cake  powder 
on  platinum  foil  over  the  Bunsen  flame,  in  the  same  way  as 
was  described  with  bones  in  paragraph  97,  until  the  ash  is 
quite  light-coloured.  Empty  the  ash  into  a  clean  test-tube 
and  fill  it  about  an  inch  deep  with  dilute  hydrochloric  acid. 
Boil  for  a  minute  or  so,  then  filter.  Spread  out  the  filter  on 
a  glass  plate  ;  grains  of  sand,  if  present,  will  be  seen  on  the 
paper.  ThiS  experiment  may  not  always  succeed  on  the 
first  attempt  owing  to  the  small  amount  which  can  be 
burnt  at  once  on  a  piece  of  foil.  Two  or  three  attempts  will 
usually  give  some  sand,  especially  if  the  same  filter  be  used 
for  all  the  experiments. 

114.  Linseed-cake. — All  the  above  tests  are  applicable 
to  any  kind  of  oil-cake,  but  some  few  tests  may  be  per- 
formed with  special  kinds  of  cake.  A  pure  linseed-cake 
may  generally  be  recognised  from  two  of  its  properties.  It 
is  highly  mucilaginous,  and  it  does  not  contain  starch. 

115.  Mucilage  in  Linseed-cake.— Place  about  a 
teaspoonful  of  ground  linseed-cake  in  a  4-ounce  beaker  and 
half-fill  the  beaker  with  boiling  water.  Stir  vigorously  with 
a  glass  rod  ;  allow  to  cool.  It  will  be  found  that  the  linseed 
has  swollen  up  into  a  gummy  mass.  The  better  the  cake, 
the  more  mucilaginous  the  mass  will  be;  whilst  a  very 
poor  cake  will  not  swell  up  at  all,  but  settle  quickly  to  the 
bottom  of  the  liquid. 


41    PRACTICAL  AGRICULTURAL  CHEMISTRY  [116-119 

*  116.  Testing  Linseed-cake  for  Starch.— Pour  a 

little  of  the  gummy  substance  prepared  in  the  last  experi- 
ment into  a  test-tube  and  boil  it.  As  soon  as  it  has  boiled 
cool  it  down  by  allowing  the  cold  water  from  a  tap  to  run 
over  the  outside  of  the  tube.  When  quite  cool  add  a  few 
drops  of  a  solution  of  iodine  in  potassium  iodide  and  shake 
up.  If  the  cake  assume  a  greenish  colour  it  is  pure  and 
free  from  starch  ;  if  it  turn  deep  blue  or  black  it  shows  the 
presence  of  starch,  and  therefore  it  has  been  adulterated. 

117.  Cotton-wool  in  Cotton-cake.— In  the  pre- 
paration of  cotton-cake  it  is  necessary  to  free  the  seed  from 
cotton-wool.  If  this  be  badly  done  the  value  of  the  cake 
will  be  much  impaired. 

Break  up  a  piece  of  undecorticated  cotton-cake,  weighing 
about  two  ounces,  as  finely  as  possible  in  a  mortar,  then  place 
it  in  a  wire  sieve  having  from  twenty  to  thirty  meshes  to  the 
linear  inch.  Shake  the  sieve  until  all  the  finer  portion  has 
passed  through,  and  examine  the  husk  which  is  left.  Should 
the  cake  be  an  inferior  one  a  small  quantity  of*  cotton-wool 
will  usually  be  found  adhering  to  it.  The  wool  may  often 
be  seen  without  this  preliminary  sifting. 

Grass  and  Hay 

118.  Grass  and  Hay. — All  the  substances  which  have 
been  shown  to  occur  in  oil-cakes  may  be  found  in  grass. 
Some  of  these,  however,  such  as  oil,  occur  in  such  small 
quantities  that  it  would  require  far  more  delicate  experiments 
than  those  detailed  in  these  pages  to  show  their  presence. 
The  following  experiments,  however,  are  instructive  and 
should  be  performed. 

119.  Albuminoids  in  Grass.— Cut  up  a  little  grass 
(or  hay)  as  finely  as  possible  with  a  pair  of  scissors  and 
grind  it  up  in  a  mortar  with  a  little  sharp  sand.  This  will 
render  it  sufficiently  fine  to  mix  readily  with  soda-lime. 
Mix  it  with  an  equal  quantity  of  soda-lime  and  heat  a  little 


120-122]  GRASS  AND   HAY  45 

of  the  mixture  in  an  ignition-tube.     The  albuminoids  will 
give  off  ammonia.     See  paragraph  85. 

120.  Chlorophyll  in  Grass.— Chlorophyll  is  the  green 
colouring  matter  which  occurs  in  grass.  Cut  up  a  handful 
of  grass  with  scissors  and  place  it  in  a  mortar ;  just  cover 
the  grass  with  methylated  spirit  and  grind  it  gently  with  the 
pestle  for  a  few  minutes.  Now  filter  the  substance  through 
a  piece  of  linen  stretched  loosely  over  the  top  of  a  beaker 
and  tied.  The  liquid  which  comes  through  will  be  quite 
green.  Pour  a  little  of  this  liquid  into  an  evaporating-basin 
and  leave  it  on  a  steam-bath  to  evaporate.  Do  not  evaporate 
over  a  Bunsen  flame,  or  it  will  catch  fire.  When  all  the 
spirit  has  evaporated  a  film  of  green  chlorophyll  will  be 
found  at  the  bottom  of  the  dish.  Now  squeeze  all  the 
spirit  out  of  the  substance  left  in  the  linen  and  wash  it  with 
a  little  ether.  The  residue  left  in  the  linen  will  be  found  to 
be  light-coloured,  and  if  the  washing  be  continued  will 
eventually  become  colourless. 

121.  Ash  in  Grass. — Place  a  handful  of  hay,  or  grass, 
dried  in  the  steam-oven,  on  a  porcelain  tile  and  light  it  with 
a  match.  When  it  has  stopped  burning  gather  all  the  ash 
on  to  a  piece  of  platinum  foil  and  heat  it  until  it  loses  its 
black  colour.  Sometimes  the  ash  thus  left  will  be  green  : 
this  is  due  to  the  presence  of  manganese,  but  more  often  it 
will  be  white  or  light-brown.  Keep  the  ash  for  the  next 
experiment. 

*  122.  Alkalies  in  Grass.— The  ash  of  grass  contains 
both  potash  and  soda,  which  will  probably  fuse  in  the 
Bunsen  flame,  and  so  cause  the  ash  to  adhere  to  the 
platinum  foil.  Roll  up  the  foil,  with  the  ash  adhering  to  it, 
and  place  in  a  test-tube.  Just  cover  it  with  distilled  water 
and  boil.  Now  take  a  drop  of  the  solution  thus  prepared, 
on  the  end  of  a  glass  rod,  and  touch  a  piece  of  red  litmus- 
paper  with  it.  Where  the  liquid  touches  the  paper  the  red 
will  be  turned  to  blue,  showing  the  presence  of  an  alkali 


46    PRACTICAL  AGRICULTURAL  CHEMISTRY   [123-126 

Keep  the  test-tube  containing  the  platinum  foil  and  liquid 
for  the  next  experiment. 

*  123.  Phosphates  in  Grass.— To  the  water  in  the 
test-tube  (paragraph  122)  add  an  equal  volume  of  dilute 
nitric  acid  and  warm.  Decant  the  liquid  into  another  clean 
test-tube,  leaving  the  platinum  foil  behind.  To  the  clear 
liquid  so  obtained  add  an  excess  of  ammonium  molybdate 
solution  and  boil ;  a  yellow  precipitate  will  appear,  showing 
that  the  grass  contained  phosphates. 

Roots 

124.  Turnips.— Roots,  such  as  turnips,  swedes,  and 
mangels,  differ  from  the  foods  which  have  been  considered, 
in  that  they  contain  a  very  much  larger  proportion  of  water 
and  a  greater  quantity  of  sugar.  When  the  water  is  squeezed 
out  of  the  roots  it  brings  the  sugar  and  other  soluble  sub- 
stances with  it.  Hence  the  components  of  a  turnip  may  be 
divided  into  two  kinds  :  the  soluble,  which  with  the  water 
constitute  juice,  and  the  insoluble,  which  go  by  the  name  of 
crude  fibre.  The  crude  fibre  is  very  much  like  hay  in  its 
constitution  ;  therefore  the  experiments  here  described  are 
intended  only  to  show  the  properties  of  the  juice. 

125.  Juice  in  Turnips.— Cut  a  turnip  up  into  six 
sections  with  a  large  knife.  Grate  up  one  or  two  of  these 
sections  on  a  bread-grater,  allowing  the  pulp  to  fall  on  to  a 
piece  of  linen  stretched  over  a  porcelain  tile.  When  a  good 
handful  of  pulp  has  been  thus  prepared,  fold  it  up  in  the 
cloth  and  squeeze  out  the  juice  into  a  beaker.  Throw  away 
the  fibre  left  in  the  cloth  and  with  the  juice  perform  the 
experiments  described  in  paragraphs  126  and  129. 

126.  Sugar  in  Turnips. — Taste  a  little  of  the  juice. 
It  has  the  flavour  of  raw  turnip,  but  is  nevertheless  very 
sweet.  Pour  sufficient  juice  into  a  clean  test-tube  to  fill 
about  half  an  inch  of  the  tube.  Dilute  this  with  about  four 
times  its  volume  of  water,  then  add  about  an  equal  volume 


127-129]  ROOTS  47 

of  strong  lead  acetate  solution.  Shake  up  well  and  allow 
to  stand  for  quarter  of  an  hour  to  settle.  Whilst  it  is  settling 
go  on  with  the  next  experiment.  At  the  end  of  the  quarter 
of  an  hour  the  liquid  in  the  test-tube  will  have  become  quite 
clear,  except  for  a  thick  deposit  of  white  material  at  the 
bottom.  Pour  off  a  little  of  the  clear  liquid  into  another 
test-tube  and  add  caustic  potash  solution  ;  a  white  precipi- 
tate will  be  caused.  Add  more  caustic  potash  until  the  pre- 
cipitate is  redissolved  ;  then  add  a  little  Fehling's  Solution, 
and  boil.  A  yellow  or  bright  red  precipitate  will  be  formed, 
which  shows  the  presence  of  sugar. 

*  127.  Cane  Sugar  and  Grape  Sugar.— The  sugar 
found  in  swedes  and  turnips  is  a  different  substance  from 
the  sugar  which  we  use  for  sweetening  purposes.  The  former 
is  glucose  or  grape  sugar,  the  latter  is  cane  sugar.  The 
properties  of  these  two  kinds  of  sugar  are  best  studied  by 
using  the  pure  substances.  Dissolve  a  little  cane  sugar  in 
water  in  a  test-tube.  In  another  test-tube  make  a  solution 
of  glucose  ;  to  each  of  these  add  a  little  Fehling's  Solution 
and  boil.  The  glucose  will  give  a  reddish  precipitate,  whilst 
the  cane  sugar  will  not. 

*  128.  Inversion  of  Cane  Sugar. — Make  a  solution 
of  cane  sugar  in  a  test-tube  half  full  of  water ;  add  a  few 
drops  of  strong  hydrochloric  acid  and  boil  well.  After 
boiling  add  a  little  potash  to  neutralise  the  acid,  then  a  little 
Fehling's  Solution,  and  boil  again.  A  precipitate  will  now 
be  formed,  showing  that  the  cane  sugar  has  been  changed 
to  glucose  by  boiling  with  the  acid. 

*  129.  Albuminoids  in  Turnip  Juice.— One  of  the 
properties  of  albuminoids  is  that  they  are  rendered  insoluble 
by  carbolic  acid.  Pour  a  tablespoonful  of  turnip  juice  into 
a  beaker  and  add  two  drops  of  strong  carbolic  acid  solution 
(80  per  cent.)  Allow  the  beaker  to  stand  overnight  The 
albuminoids  will  settle,  leaving  the  liquid  clear. 


48    PRACTICAL  AGRICULTURAL   CHEMISTRY   [130-132 

Cereal  and  Leguminous  Foods 

130.  The  most  important  cereal  and  leguminous  foods 
are  wheat,  barley,  oats,  maize,  peas,  and  beans.  These  focds 
should  be  tested  for  their  main  constituents,  viz.  water,  oil, 
albuminoids,  and  carbohydrates,  by  the  methods  described 
in  paragraphs  108,  109,  no,  and  m;  noting  at  the  same 
time  the  relatively  large  quantities  of  albuminoids  in  peas, 
and  beans,  and  of  carbohydrates  in  wheat,  barley,  oats, 
and  maize.  Wheat  differs  from  other  foods  in  containing 
a  nitrogenous  substance,  called  gluten,  which  gives  wheaten 
flour  the  peculiar  property  of  kneading  with  water.  All  the 
cereals  contain  large  quantities  of  starch. 

131.  Starch  in  Flour. — The  test  for  starch  has  already 
been  given  (116).  Wet  a  little  flour  with  water  so  as  to  make 
a  thin  cream.  Boil  a  little  water  in  a  test-tube,  and  when 
it  is  boiling  briskly  add  a  drop  of  the  cream,  then  boil  for  a 
few  seconds.  Cool  the  liquid  by  allowing  a  current  of  cold 
water  to  flow  from  a  tap  round  the  outside  of  the  test-tube, 
and  when  quite  cold  add  a  drop  of  iodine  solution.  An 
immediate  deep-blue  coloration  indicates  the  presence  of 
starch.  The  colour  will  appear  almost  black,  but  if  a  drop 
of  the  dark  liquid  be  mixed  with  a  large  quantity  of  water 
it  will  be  seen  that  it  really  is  of  a  dark-blue  colour. 

132.  Gluten  in  Wheaten  Flour.— Mix  a  handful 
of  wheaten  flour  with  enough  water  to  form  a  stiff  paste. 
Knead  it  well  in  the  fingers,  then  wrap  it  up  in  a  small 
piece  of  muslin  and  hold  it  in  a  gentle  stream  of  water  from 
a  tap,  kneading  it  all  the  time.  The  starch  will  be  gradually 
washed  away  through  the  muslin,  leaving  a  dark-coloured 
indiarubber-like  mass.  This  is  gluten,  which  gives  a  mixture 
of  flour  and  water  its  peculiar  adhesiveness. 


133-137]  DAIRY    PRODUCE  49 

DAIRY  PRODUCE 

Milk 

133.  Action  of  Acid  on  Milk.— Half  fill  a  test-tube 
with  milk.  Add  about  six  drops  of  dilute  sulphuric  acid 
and  shake.  Allow  the  tube  with  its  contents  to  stand  for 
five  minutes.  At  the  end  of  that  time  the  milk  will  be  seen 
to  have  curdled.  The  acid  has  coagulated  the  soluble 
albuminoids,  rendering  them  insoluble,  and  thus  forming 
clots  which  separate  out  from  the  milk. 

134.  Fat  in  Milk.— Filter  the  curdled  milk  and  save 
the  clear  filtrate  (136).  Spread  out  the  filter-paper  which 
contains  the  'curd'  on  a  glass  plate  and  place  in  the 
steam-oven  to  dry.  When  it  has  got  quite  dry  the  fat  will 
melt  out  of  the  curd,  and  form  grease  stains  on  the  filter- 
paper. 

135.  Albuminoids  in  Milk.— The  residue  left  on  the 
filter-paper,  after  the  fat  has  been  melted  out  as  described 
in  the  last  experiment,  is  principally  albumen  and  casein. 
Both  these  substances  contain  nitrogen,  which  may  be 
tested  for  by  scraping  this  residue  off  the  filter,  mixing  with 
soda-lime,  and  heating  in  an  ignition-tube  as  described  in 
paragraph  85  ;  ammonia  will  be  given  off. 

136.  Sugar  in  Milk. — The  clear  liquid  which  has 
been  saved  (134)  contains  sugar.  This  sugar  is  different 
from  either  cane  sugar  or  glucose,  and  goes  by  the  name 
of  lactose,  or  milk  sugar.  It  has  an  action,  however,  on 
Fehling's  Solution  (266)  similar  to  that  of  glucose.  Add 
to  the  clear  liquid  in  the  test-tube  (134)  a  little  potassium 
hydrate  solution  until  the  liquid  is  no  longer  acid,  then  add 
Fehling's  Solution  and  boil;  a  yellow  precipitate  will  be 
formed,  indicating  the  presence  of  sugar. 

137.  Natural  Acidification  of  Milk.— If  milk  is 
allowed  to  stand  in  the  air,  certain  bacteria  will  gradually 


50     PRACTICAL  AGRICULTURAL  CHEMISTRY  ("138-139 

oxidise  the  lactose,  producing  lactic  acid.  This  acid  will 
curdle  the  milk,  as  described  in  paragraph  133. 

The  milk  may  be  prevented  from  '  going  sour '  in  various 
ways : 

(a)  By  heat  or  cold,  thus  destroying  the  bacteria  or 
suspending  their  activity. 

(6)  By  adding  an  alkali,  e.g.  carbonate  of  soda,  so 
neutralising  the  acid  as  it  is  produced. 

(c)  By  adding  a  'germicide,'  such  as  borax,  boracic 
acid,  or  formalin,  to  poison  the  bacteria. 

As,  however,  it  is  illegal  to  add  any  foreign  substances 
to  milk,  heat  and  cold  are  the  only  two  methods  officially 
recognised. 

138.  Preservation  of  Milk.— Half  fill  six  test-tubes 
with  milk,  and  treat  as  follows  :  Allow  the  first  portion 
to  remain  in  the  test-tube  stand  without  any  further  treat- 
ment. Boil  the  second  portion  and  place  it  also  in  the 
test-tube  stand.  To  the  third  add  a  few  drops  of  forma- 
lin (40  per  cent,  formic  aldehyde) ;  to  the  fourth  add  a 
few  drops  of  strong  sodium  carbonate  solution  ;  and  to 
the  fifth  a  few  drops  of  borax  solution.  The  sixth  must 
be  placed  in  an  ice-chest  so  that  it  may  remain  at  a  low 
temperature. 

The  milk  should  be  examined  daily,  and  the  order  in 
which  the  different  samples  turn  sour  noted.  The  record 
so  obtained  will  give  an  indication  of  the  efficiency  of  the 
various  methods  employed. 

139.  Tests  for  Preservatives  in  Milk.— The  pre- 
servatives usually  found  in  milk  are  boracic  acid,  borax, 
and  formalin.  The  following  tests  should  be  applied  to 
samples  of  fresh  milk;  if  no  results  are  obtained,  they 
should  be  repeated  with  samples  treated  as  described  in 
paragraph  138. 

Boracic  Acid  or  Borax. — Make  the  milk  alkaline  with 
lime   water,  evaporate  to   dryness  and  ignite  until  the  re- 


140-141]  DAIRY   PRODUCE  5 1 

sidue  becomes  white.  Warm  the  ash  with  a  few  drops  of 
strong  hydrochloric  acid.  Evaporate  the  filtrate  to  dryness 
and  dissolve  the  residue  in  a  few  drops  of  water.  Place  in 
the  dish  a  piece  of  turmeric  paper  and  evaporate  to  dry- 
ness on  the  water-bath.  A  brown  colour  which  turns 
dark  green  with  ammonia  indicates  boracic  acid. 

Formaldehyde. — Place  about  10  c.c.  of  the  milk  and  an 
equal  volume  of  strong  hydrochloric  acid  in  an  evaporating 
basin.  Add  one  drop  of  very  dilute  ferric  chloride.  Heat 
slowly  with  constant  stirring  to  a  temperature  a  little  below 
boiling.  A  violet  colour  indicates  the  presence  of  formalin. 
Care  should  be  taken  not  to  boil  the  milk  or  the  colour  may 
be  destroyed. 

Note. — This  test  may  be  used  for  the  presence  of 
formalin  in  other  substances  than  milk,  but  as  the  proteids 
of  milk  take  part  in  the  reaction  a  few  c.c.  of  pure  milk 
must  be  added  to  the  suspected  liquid  before  the  test  is 
applied. 

Butter 

Butter  consists  principally  of  the  fat  of  the  milk,  but 
it  also  contains  small  quantities  of  curd,  salt,  and  water. 

140.  Water  in  Butter. — Place  as  much  butter  as 
you  conveniently  can  in  a  test-tube.  Then  hold  the  tube  in 
hot  water  until  the  butter  is  completely  melted.  Note  the 
appearance  of  the  tube.  The  pure  butter-fat  will  form  a 
clear  top  layer.  Beneath  this  will  come  a  cloudy  layer 
containing  the  curd  and  salt,  and  beneath  this,  again,  will 
be  seen  drops  of  water. 

141.  Curd  in  Butter. — Whilst  the  butter  is  still  hot 
pour  it  on  to  a  dry  filter-paper  in  a  funnel.  Place  the  funnel 
in  the  neck  of  a  4-oz.  conical  flask  and  place  the  whole 
arrangement  in  the  steam-oven  (22).  This  will  serve  to 
keep  the  butter  melted  whilst  it  is  filtering.  In  a  few 
minutes  nothing  will  be  left  on  the  paper  but  the  curd  and 

£2 


52    PRACTICAL  AGRICULTURAL  CHEMISTRY  [142-144 

salt  with  a  little  water.  The  curd  may  be  shown  to  contain 
nitrogen  by  heating  with  soda-lime  as  described  in  para- 
graph 85. 

142.  Salt  in  Butter. — Hold  the  greasy  filter-paper 
prepared  in  the  last  experiment,  together  with  its  contents, 
by  means  of  a  pair  of  crucible  tongs  over  a  porcelain  tile, 
then  light  it  with  the  flame  of  a  Bunsen.  When  it  has 
quite  burned,  and  the  ash  has  fallen  on  to  the  tile,  sweep  it 
up  into  a  test-tube.  Half  fill  the  test-tube  with  water  and 
boil  for  a  minute  or  two,  then  filter.  The  clear  liquid  which 
comes  through  will  contain  any  salt  which  was  present  in 
the  original  butter.  To  test  for  salt  add  a  drop  of  dilute 
nitric  acid  and  a  few  drops  of  silver  nitrate  solution.  A 
white  precipitate  will  be  formed  (see  paragraph  201). 

Cheese 

Cheese  contains  exactly  the  same  constituents  as  butter, 
but  in  different  proportions.  Thus  whilst  the  butter  consists 
principally  of  fat  the  cheese  consists  chiefly  of  curd. 

143.  Fat  in  Cheese. — Place  a  few  cheese-parings  on 
a  piece  of  filter-paper  and  heat  in  the  steam-oven  (22).  The 
fat  in  the  cheese  will  melt  and  grease  the  paper. 

144.  Albuminoids  in  Cheese.— Heat  a  little  of  the 
cheese  with  soda-lime  as  described  in  paragraph  85.  The 
presence  of  nitrogen  is  shown  by  the  evolution  of  ammonia. 


145-146]  QUALITATIVE  ANALYSIS  53 


SECTION    IV 

QUALITATIVE  ANALYSIS  OF  THE  BODIES 
COMMONLY  OCCURRING  IN  SOILS  AND  MANURES 

Introductory  Remarks 

145.  This  section  treats  only  of  those  bodies  which 
occur  in  soils,  manures,  and  agricultural  products,  namely, 
the  carbonates,  sulphates,  chlorides,  nitrates,  nitrites,  sili- 
cates, and  phosphates  of  the  metals  aluminium,  iron,  manga- 
nese, calcium,  magnesium,  potassium,  sodium,  and  ammo- 
nium, together  with  organic  carbon,  nitrogen,  chlorine,  and 
sulphur. 

Chemical  formulae  are  freely  used,  but  not  unless  the 
name  of  the  compound  has  already  been  mentioned  in  the 
same  paragraph. 

In  some  instances  the  chemical  changes  are  expressed 
by  equations. 

146.  The  systematic  name  of  an  inorganic  compound 
such  as  a  salt  is  usually  a  double  name,  the  metal  forming 
one  portion,  and  the  acid  portion  (called  the  acid-radical) 
the  other  portion  of  the  name.  Thus  sodium  on  being 
added  to  sulphuric  acid  would  form  sodium  sulphate  : — 

Na2     +     H2S04 

Sodium  Sulphuric 

acid 

Hence  the  names  of  both  metal  and  acid,  or  some  modifi- 
cation of  them,  are  included  in  the  name  of  the  compound 
formed.  In  analysis  it  is  found  convenient  to  test  for  the 
metal  and  the  acid-radical  separately.     In  the  above  case  of 


sa 

Na2S04 

+     H2 

Sodium 

Hydrogen 

sulphate 

54    PRACTICAL  AGRICULTURAL  CHEMISTRY  [147-150 

sodium  sulphate,  the  sodium  (Na)  would  first  be  tested  for 
by  the  sodium  test  (186),  and  then  the  acid  radical  (S04) 
would  be  tested  for  by  the  sulphate  test  (194). 

147.  It  will  be  noticed  that  the  name  of  a  suitable  sub- 
stance for  performing  the  tests  upon  is  given  at  the  head 
of  each  series  of  reactions.  Thus,  when  testing  for  sodium, 
the  most  suitable  substance  to  use  is  sodium  chloride 
(NaCl).  The  reagent  to  be  added  is  given  immediately 
after  the  paragraph  number. 

148.  Entry  in  Note-book. — A  note-book  of  quarto 
size  should  be  used.  A  concise  account  of  each  experiment 
or  test  should  be  entered  directly  it  is  made.  Neat  pencil 
entry  will  suffice.  The  entry  should  not  be  considered 
complete  until  after  it  has  been  examined  and  initialled  by 
the  teacher. 

The  following  tests  for  sodium  will  serve  for  an  example 
of  entry  : — 

Sodium  (Na).    Used  NaCl. 

% 
Dipped  a  platinum  wire  into  the  solution  and  held  in  Bunsen  flame : 

golden-yellow  flame-coloration  ;  not  seen  through  prism. 

Heated  the  solid  in  ignition-tube  :  decrepitated  and  finally  fused  ; 

no  sublimate  formed. 


General  Rules  to  be  Observed  whilst  Working 

149.  Before  commencing  work  see  that  the  reagent- 
bottles  are  full ;  filter  any  liquids  that  require  it.  Clean  the 
apparatus  if  necessary.  It  is  far  better  to  put  everything 
away  clean.  Keep  the  bench  scrupulously  clean  during 
work. 

150.  In  cleaning  apparatus,  glass  and  porcelain  can 
usually  be  cleansed  by  washing  with  a  brush.  If  this  fails 
caustic  alkalies  or  acid  may  be  requisite.  Failing  these, 
rubbing  or  shaking  with  a  little  sea-sand  will  usually  suffice. 


151-158]  TESTS   FOR   THE   METALS  55 

Metal  vessels  are  best  cleaned  with  a  little  moistened  sea- 
sand. 

151.  When  using  a  reagent  bottle  the  bottle  should  be 
grasped  by  the  right  hand,  and  the  stopper  taken  out  by  the 
left  hand.  After  use  replace  the  stopper  and  put  back  the 
bottle  on  the  shelf.  In  this  way  the  bottle  is  not  placed  on 
the  bench  at  all,  and  much  time  is  saved. 

152.  Brass  crucible  tongs  must  not  be  used  for  holding 
vessels  containing  acid  liquids,  or  the  brass  may  be  dissolved 
and  introduced  into  the  liquid.  Platinum  crucibles  must 
not  be  handled  by  brass  tongs  when  red-hot. 

153.  When  heating  liquids  in  porcelain  or  glass  the 
flame  should  never  reach  higher  than  the  level  of  the  liquid, 
or  the  vessel  will  break. 

154.  Liquids  only  are  to  be  poured  down  the  sink ; 
solids  and  filter-papers  should  be  placed  in  boxes  or  baskets. 

155.  Crucibles  or  vessels  containing  solids  are  best 
heated  on  pipeclay  supports,  flasks  containing  liquids  on 
wire  gauze. 

156.  When  an  operation  is  unfinished  the  vessels  con- 
taining the  substances  should  be  labelled  before  putting 
them  away.     Never  trust  to  memory  in  these  matters. 

157.  Before  commencing  any  operation  read  carefully 
through  the  whole  of  the  description. 


REACTIONS  FOR  THE  METALS 


ALUMINIUM  (Al).— Use  alum,  AlK(S04)2.i2H20,  or 
ammonia-alum,  AlNH4(S04)2.i2H20,  solution. 

158.  Ammonium  Hydrate  (NH4OH)  gives  a  white 
gelatinous  precipitate  of  aluminium  hydrate,  Al(OH)3. 
This  precipitate  is  somewhat  soluble  in  a  larger  excess  of 


$6   PRACTICAL  AGRICULTURAL   CHEMISTRY    [159-164 

NH4OH  ;  hence  this  reagent  should  only  be  added  in  slight 
excess.  Al(OH)3  is  readily  soluble  in  hydrochloric  acid 
(HC1)  and  in  acetic  acid  (HA). 

159.  Potassium  Hydrate  (KHO)  or  Sodium 
Hydrate  (NaHO)  when  added  drop  by  drop  gives  the 
same  precipitate  as  NH4OH,  but  it  is  readily  soluble  in 
excess  of  these  reagents.  By  adding  ammonium  chloride 
(NH4C1)  in  large  excess  to  this  solution,  and  boiling,  the 
precipitate  will  be  thrown  down  again. 

160.  Ammonium  Sulphide,  (NH4)2S,  gives  the 
same  precipitate  as  NH4OH  with  evolution  of  sulphuretted- 
hydrogen  gas.  This  precipitate  is  insoluble  in  excess  of 
the  reagent.  

IRON  (Fe).— Use  ferrous  sulphate  (FeS04.7H20)  and 
ferric  chloride  (Fe2Cl6)  solutions. 

161.  Note Iron  forms  two  classes  of  compounds,  known  respec- 
tively as  ferrous  and  ferric  compounds.  It  is  often  necessary  that  the 
analyst  should  ascertain  whether  one  or  both  of  these  two  classes  are 
present  in  a  substance  containing  iron.  Tests  are  here  given  for  both 
classes. 

FERROUS  SALTS. — Use  ferrous  sulphate 
(FeS04.7H20). 

162.  Ammonium  Hydrate  (NH4OH)  or  potassium 
hydrate  (KHO)  gives  a  dingy  green  precipitate  of  ferrous 
hydrate,  Fe(OH)2,  which  becomes  brown  on  exposure  to 
the  air.  It  is  soluble  in  hydrochloric  acid  (HC1),  and  in- 
soluble in  excess  of  KHO. 

163.  Ammonium  Sulphide,  (NH4)2S,  gives  a  black 
precipitate  of  ferrous  sulphide  (FeS),  soluble  in  hydro- 
chloric acid  (HC1). 

164.  Potassium  Ferrocyanide,  K4Fe(CN)6,  gives 
a  light- blue  precipitate,  becoming  dark  on  exposure  to  the 
air. 


165-173]  TESTS   FOR  THE   METALS  57 

165.  Potassium  Ferricyanide,  K3Fe(CN)6,  gives 
a  dark-blue  precipitate,  soluble  in  HC1. 

166.  Potassium  Sulphocyanide  (KCNS)  produces 
no  change  in  ferrous  solutions  if  free  from  ferric  salts. 


FERRIC  SALTS.— Use  ferric  chloride  (FeCl)3. 

167.  Ammonium  Hydrate  (NH4OH)  or  Potas- 
sium Hydrate  (KHO)  gives  a  reddish-brown  flocculent 
precipitate  of  ferric  hydrate,  Fe(OH)3,  soluble  in  hydro- 
chloric acid  (HC1),  insoluble  in  excess  of  AmHO  and  KHO. 

168.  Ammonium  Sulphide,  (NH4)2S,  gives  a  black 
precipitate  of  ferrous  sulphide  (FeS),  which  contains  white 
sulphur  (S).     The  black  FeS  hides  the  white  S  from  view. 

169.  Potassium  Ferrocyanide,  K4Fe(CN)6,  gives 
a  dark-blue  precipitate  of  Prussian  blue,  soluble  in  oxalic 
acid,  turned  brown  by  potassium  hydrate  (KHO). 

170.  Potassium  Ferricyanide,  K3Fe(CN)6,  gives 
no  precipitate,  but  the  liquid  darkens  in  colour. 

171.  Potassium  Sulphocyanide  (KCNS)  gives  a 
blood-red  coloration,  which  may  be  destroyed  by  the  addi- 
tion of  mercuric  chloride  (HgCl2). 

172.  By  heating  a  small  portion  of  solid  ferric  or 
ferrous  salt  on  the  borax  bead  (27)  in  the  outer  blowpipe 
flame  a  reddish-brown  colour  is  obtained  whilst  the  bead  is 
hot,  which  fades  on  cooling.  The  inner  flame  gives  an 
olive-green  bead  both  hot  and  cold. 


MANGANESE  (Mn).— Use  manganous  sulphate 
(MnS04)  solution. 

173.  Ammonium  Hydrate  (NH4OH)  gives  a  white 
precipitate  of  manganous  hydrate,  Mn(OH)2,  which  quickly 


53    PRACTICAL  AGRICULTURAL  CHEMISTRY    [174-180 

turns  brown  in  the  air.  This  is  best  seen  by  pouring  the 
precipitate  on  to  a  filter-paper.  If,  however,  ammonium 
chloride  (NH4C1)  has  been  added  before  the  NH4OH,  the 
precipitate  will  not  be  formed. 

174.  Potassium  Hydrate  (KHO)  gives  the  same 
precipitate  as  ammonium  hydrate,  even  in  the  presence  of 
AmCl. 

175.  Ammonium  Sulphide,  (NH4)2S,  gives  a  flesh- 
coloured  precipitate  of  manganous  sulphide  (MnS).  This 
precipitate  often  appears  yellow  from  the  excess  of  the 
(NH4)2S,  which  has  been  added.  On  filtering  off  this  liquid 
the  true  colour  may  be  seen.  The  colour  of  the  precipi- 
tate darkens  on  standing  in  the  air. 

176.  If  a  solid  substance  containing  manganese  be 
mixed  with  three  times  its  weight  of  sodium  carbonate 
(Na2C03),  and  a  third  as  much  potassium  nitrate 
(KNO3),  and  tne  mixture  fused  on  platinum  foil,  a  bluish- 
green  mass  is  obtained  on  cooling. 

177.  Borax  Bead  (27). — In  the  outer  flame  violet 
whilst  hot,  amethyst  when  cold.  In  the  inner  flame  colour- 
less both  hot  and  cold. 


CALCIUM  (Ca).— Use  calcium  chloride  (CaCl2'6H20) 
solution. 

178.  Ammonium  Carbonate,  (NH4)2C03,  added 
after  ammonium  chloride  (NH4C1)  gives  a  white  precipitate 
of  calcium  carbonate  (CaC03),  soluble  in  acetic  acid. 

179.  Ammonium  Oxalate,  (NH4)2C204,  gives  a 
white  precipitate  of  calcium  oxalate  (CaC204)  soluble  in 
hydrochloric  acid  (HC1),  and  insoluble  in  acetic  acid  (HA). 

180.  Sulphuric  Acid  (H2S04)  gives  a  white  preci- 
pitate of  calcium  sulphate  (CaS04),  which  forms  at  once  in 
strong  solutions,  but  only  on  being  boiled,  in  dilute  solutions. 


181-187]  TESTS  FOR  THE  METALS  59 

This  precipitate  is  slightly  soluble  in  water,  but  less  so  in 
alcohol.  If  the  precipitate  is  not  formed  on  boiling,  it  will 
come  down  on  cooling  and  adding  excess  of  alcohol. 

181.  Flame  Coloration  (26).— If  a  clean  piece  of 
platinum  wire  is  dipped  into  the  liquid,  and  then  held  in 
the  Bunsen  flame,  a  bright  reddish-yellow  colour  will  appear. 


MAGNESIUM  (Mg). — Use  magnesium  sulphate 
(MgS04.7H20)  solution. 

182.  Sodium  Phosphate  (Na2HP04)  added  after 
ammonium  chloride  (NH4C1)  and  ammonium  hydrate 
(NH4OH)  gives  a  white  crystalline  precipitate  of  magnesium- 
ammonium  phosphate  (MgNH4P04.6H20),  soluble  in  acids. 

183.  Potassium  Hydrate  (KHO)  gives  a  white  pre- 
cipitate of  magnesium  hydrate,  Mg(OH)2,  soluble  in  acids. 

184.  Ammonium  Hydrate  (NH4OH)  gives  the 
same  precipitate  as  potassium  hydrate ;  but  if  ammonium 
chloride  (NH4C1)  be  added  previously,  this  precipitate  will 
not  form. 

185.  Ammonium  Carbonate  (NH4)2C03  gives  a 
white  precipitate  of  basic  magnesium  carbonate  in  strong 
solutions.  Ammonium  chloride  (NH4C1)  prevents  the  for- 
mation of  this  precipitate. 


SODIUM  (Na). — Use  sodium  chloride  (NaCl)  solution. 

186.  Flame  Coloration  (26). — Intense  yellow.  This 
colour  is  almost  invisible  when  viewed  through  the  indigo 
prism  or  a  thick  piece  of  cobalt-blue  glass. 

187.  Solid  sodium  chloride  heated  in  an  ignition-tube 
generally  decrepitates  and  flies  out  of  the  tube ;  but  if  it  is 
perfectly  dry  it  will  fuse,  giving  off  no  fumes. 


60    PRACTICAL   AGRICULTURAL  CHEMISTRY   [188-193 

POTASSIUM  (K). — Use  potassium  chloride  (KG) 
solution. 

188.  Platinum  Chloride  (PtCl4)  added  to  some  of 
the  potassium  chloride  in  a  watch-glass  and  stirred  with 
a  glass  rod,  gives  a  yellow  crystalline  precipitate  of 
potassium  platinum  chloride  (K2PtCl6).  The  precipitate 
forms  only  in  moderately  strong  solutions,  and  is  hastened 
by  the  addition  of  alcohol. 

188a.  Sodium  Picrate  added  to  a  little  KC1  solution 
placed  in  a  watch-glass  gives  golden  yellow  needle-like 
crystals  of  potassium  picrate.  The  reaction  is  promoted 
by  addition  of  alcohol  and  stirring. 

189.  Flame  Coloration  (26).— Pale  violet.  When 
viewed  through  the  indigo  prism  or  cobalt-blue  glass  the 
colour  appears  crimson.  This  colour  is  seen  through  the 
prism  in  the  presence  of  sodium  salts. 

190.  Potassium  chloride  heated  on  platinum  foil  behaves 
exactly  like  sodium  chloride. 


AMMONIUM  (NHj). — Use  ammonium  chloride 
(NH4C1)  solution, 

191.  Potassium  Hydrate  (KHO)  poured  either  into 
the  solution  or  on  to  some  solid  ammonium  chloride  in  a 
test-tube  and  heated,  gives  off  ammonia  gas  (NH3),  which 
may  be  recognised  by  its  smell,  or  by  holding  a  piece  of 
moistened  yellow  turmeric-paper  over  the  mouth  of  the  test- 
tube,  when  it  will  be  turned  brown. 

192.  Platinum  Chloride  (PtCl4)  stirred  in  a  watch- 
glass  with  the  solution  gives  a  yellow  crystalline  precipitate. 

192a.  Sodium  Picrate,  when  stirred  with  AmCl 
solution,  gives  golden-yellow  needle-like  crystals  (188a). 

193.  Solid  ammonium  chloride,  if  heated  in  an  ignition- 
tube,  volatilises  completely,  and  forms  a  white  sublimate  on 
the  cold  part  of  the  tube. 


194-197]  TESTS   FOR   ACID-RADICALS  6l 


REACTIONS   FOR  THE  ACIDS. 


SULPHATE  ("S04). — Use  sodium  sulphate 
(Na2S04.i2H20)  solution. 

194.  Barium  Chloride  (BaCl2)  gives  a  white  precipi- 
tate of  barium  sulphate  (BaS04),  insoluble  in  acids. 


CARBONATE  ("COa).— Use  sodium  carbonate 
(Na2C03.ioH20)  solution. 

195.  Hydrochloric  Acid  (HC1)  causes  carbon  dioxide 
gas  (C02)  to  come  off  with  effervescence.  This  gas  may 
be  recognised  either  by  dipping  a  glass 
rod  into  lime-water  and  holding  the 
wet  end  of  it  just  inside  the  test-tube  ; 
the  adhering  lime-water  will  be  ren- 
dered milky  from  the  formation  of  cal- 
cium carbonate  (CaC03) ;  or  better  by  Fig.  23 
pouring  the  C02  gas  into  another  test-tube  containing  a 
little  lime-water  (fig.  23),  and  then  shaking  up,  when  the  lime- 
water  will  become  milky. 


NITRITES  ('N02).— -Use  potassium  nitrite  (KN02) 
solution. 

196.  Dilute  Sulphuric  Acid  (H2S04)  on  warming 
gives  off  brown  nitrous  fumes. 

197.  Potassium  Iodide  (KI)  Solution  and  several 
drops  of  starch  solution  on  addition  to  the  liquid  made  acid 
with  acetic  acid  gives  a  deep-blue  coloration. 


62    PRACTICAL  AGRICULTURAL  CHEMISTRY   [.198-203 

NITRATE  (N08).—  Use  potassium  nitrate  (KN03). 

198.  Ferrous  Sulphate  (FeS04)  Solution  when 

carefully  added  to  the  above  solution,  previously 

mixed  with  its  own  volume  of  strong  sulphuric 

acid  and  cooled,  will  form  a  brown  ring  where 

the  two  layers  join  (fig.  24).     This  brown  colour 

is  destroyed  by  heat ;  hence  the  tube  must  be 

kept  quite  cold  during  this  test. 

109.  Copper  Turnings  (Cu)  added,  after 

acidifying  with  strong  sulphuric  acid  (H2S04), 

gives  off  brown  fumes   either   at   once   or   on 

warming  the  tube. 

200.  Heated  with  indigo  and  sulphuric  acid 

the   indigo   is   bleached.     The   most  accurate 

method  of  applying  this   test  is  described  in 

paragraph  87. 
Fig.  24      r      °    r 


CHLORIDE  ('Cl).-Use  sodium  chloride  (NaCl)  solution. 

201.  Silver  Nitrate  (AgN03)  gives  a  pure  white  pre- 
cipitate of  silver  chloride  (AgCl),  soluble  in  ammonium 
hydrate  (NH4OH),  and  insoluble  in  nitric  acid  (HN03). 

Filter  off  a  little  of  the  precipitate  and  expose  the  filter- 
paper  containing  the  precipitate  near  a  window :  it  will  be 
darkened  by  the  action  of  the  light. 

202.  Strong  Sulphuric  Acid  (H2S04)  warmed  with 
solid  sodium  chloride  gives  off  copious  fumes  of  hydro- 
chloric acid  (HC1),  which  redden  blue  litmus-paper. 

203.  The  solid  mixed  with  manganese  dioxide  (Mn02) 
and  strong  sulphuric  acid  gives  off  a  green  gas,  chlorine  (CI), 
which  bleaches  moist  red  litmus-paper. 


204-210]  TESTS   FOR   ACID-RADICALS  63 

PHOSPHATE  ("'P04).— Use  sodium-hydrogen-phosphate 
(Na2HP04.i2H20)  solution. 

204.  Magnesium  Sulphate  (Mg2S04)  to  which 
has  been  added  ammonium  chloride  (NH4C1)  and  a 
little  ammonium  hydrate  (NH4OH),  gives  a  white  crystal- 
line precipitate  of  magnesium  -  ammonium  phosphate 
(MgNH4P04.6H20),  soluble  in  acids. 

205.  Ferric  Chloride  (FeCl3)  added  after  acetic 
acid  and  sodium  acetate  gives  a  pale  yellow  precipitate  of 
(erric  phosphate  (FeP04),  soluble  in  hydrochloric  acid. 

206.  Ammonium  Molybdate  (NH4HMo04)  when 
warmed  with  a  little  phosphate  solution  gives  a  yellow 
precipitate.  The  ammonium  molybdate  should  be  in  large 
excess,  and  the  solution  should  be  acidulated  with  nitric  acid. 

207.  Silver  Nitrate  (AgN03)  gives  a  yellow  precipi- 
tate, soluble  in  ammonium  hydrate  (NH4OH)  or  in  nitric 
acid  (HN03). 


SILICATE  (""Si04).— Use  sodium  silicate  (Na2Si03)  solu- 
tion for  liquid,  and  finely  ground  sand  (Si02)  for  solid. 

208.  Hydrochloric  Acid  (HC1)  gives  a  gelatinous 
precipitate  of  silicic  acid  (H4Si04).  This,  however,  some- 
times remains  in  solution,  in  which  case  the  liquid  should 
be  evaporated  to  dryness  in  a  basin,  moistened  with  strong 
hydrochloric  acid,  and  boiled  with  water.  An  insoluble 
residue  of  silica  (Si02)  will  remain. 

209.  If  solid  silica  (Si02)  be  fused  into  a  bead  of  sodium 
carbonate  it  causes  the  melted  bead  to  froth,  from  the 
liberation  of  carbon  dioxide. 

210.  If  solid  silica  be  fused  into  a  bead  of  microcosmic 
salt  (NaNH4HP04)  it  is  not  dissolved,  but  floats  about  in 
semi-transparent  particles. 


64    PRACTICAL  AGRICULTURAL  CHEMISTRY   [211-215 


TESTS  FOR  CARBON,  NITROGEN,   CHLORINE, 
AND   SULPHUR  IN  ORGANIC  COMPOUNDS 


CARBON  (C).— Use  sugar. 

211.  Heated  on  platinum  foil,  carbonaceous  substances 
generally  blacken,  from  the  separation  of  carbon.  On  con- 
tinued heating  the  black  substance  burns  away. 

212.  Copper  Oxide  (CuO),  when  heated  with  any 
substance  containing  carbon,  sets  free  carbon  dioxide.  To 
perform  this  experiment  mix  a  little  sugar  with  three  times 
its  bulk  of  copper  oxide  and  place  at  the  bottom  of  a  dry 
test-tube ;  cover  with  a  little  CuO.  Fit  a  tube  bent  twice 
at  right  angles  through  the  cork ;  let  this  tube  dip  into 
another  test-tube  containing  lime-water,  and  heat  the  mix- 
ture.    The  lime-water  will  become  milky. 

NITROGEN  (N).— Use  urea,  CO(NH2)2. 

213.  Soda-lime,  on  heating  with  most  nitrogenous 
substances,  liberates  ammonia,  which  may  be  recognised 
by  its  smell  and  its  action  on  turmeric-paper. 

214.  Sodium  (Na)  forms  sodium  cyanide  when  heated 
in  a  test-tube  with  most  organic  nitrogenous  substances. 
On  extracting  with  water,  filtering,  and  adding  a  solution  of 
ferrous  sulphate  containing  a  drop  of  ferric  chloride  and 
finally  hydrochloric  acid  in  excess,  a  precipitate  of  Prussian 
blue  is  left. 

CHLORINE  (CI).— Use  chloral  hydrate. 

215.  Lime  (CaO)  when  heated  in  a  test-tube  with  an 
organic-chlorine  compound  forms  calcic  chloride  (CaCl2). 
On  dissolving  in  dilute  nitric  acid  (HN03),  filtering,  and 
adding  silver  nitrate  (AgN03),  a  white  precipitate  is  formed. 


216-221]  PRELIMINARY  EXAMINATION  FOR  METALS  65 

SULPHUR  (S).— Use  albumen. 

2l6.  Boiled  with  dilute  hydrochloric  acid  (HC1)  and 
potassic  chlorate  (KC103)  until  the  solution  is  colour- 
less, sulphuric  acid  is  formed,  which  may  be  tested  for  by 
barium  chloride,  when  a  white  precipitate  will  be  formed 
(i94). 


TABLES  FOR  QUALITATIVE  ANALYSIS 

The  following  Tables  give  the  order  in  which  the  tests  should 
be  applied  for  the  metals  and  acid-radicals  treated  of  in 
the  preceding  pages.  A  number  of  analyses  should  be 
performed  by  the  student  including  limestone,  different 
varieties  of  soils,  simple  and  complex  manures,  and  the 
ashes  of  plants. 

TABLE  I.-PRELIMINARY  EXAMINATION  OF 
SOLID  SUBSTANCES  FOR  METALS 

217.  Carefully  note  the  appearance  of  the  solid,  such  as  shape, 
colour,  smell,  hardness,  &c. 

218.  If  a  solution  is  being  analysed  it  will  be  necessary,  before 
proceeding  with  this  examination,  to  evaporate  a  portion  of  the  liquid 
to  dryness  and  to  use  the  dry  residue. 

219.  Before  applying  the  following  tests  finely  powder  some  of 
the  substance,  using  an  agate  mortar  if  it  should  be  very  hard. 


Experiment 

Observation 

Inference 

220.  Expt.  I.— Heat 

I.  The    substance    fuses 

Salts  of  K  and 

in  a  small  test-tube 

and  solidifies  on  cool- 

Na or  cer- 

or igniMon-tube 

ing 

tain  salts  of 
Ca  and  Mg 

2.   It  sublimes 

Ammonium 
salts 

821. — Confirm  by  heating 

Ammonia  gas  is  given  off  which 

Ammonium  pre- 

with potassium  hydrate 

turns    moistened      turmeric- 

sent 

solution 

paper  brown 

3.  Water  is  given  off 

Presence      of 

combined 

water 

4.  It  blackens 

Presence      of 

organic  matter 

£6   PRACTICAL   AGRICULTURAL  CHEMISTRY    [222-227 


"Experiment 

Observation 

Inference 

222.  Expt.  2.— Take 

I.   Intense  yellow  colora- 

Sodium 

up  a  little  of  the 

tion 

Potassium  also 

substance  on  a  loop 

A  crimson  flame  is  seen 

present 

of  platinum  wire, 

when    viewed    through 

moisten  with  strong 

cobalt  glass  or  indigo 

HC1,  and  hold  in 

prism 

the  Bunsen  flame 

2.  Pale     violet,    crimson 
through  indigo  prism 

Potassium 

3.  Orange-red  coloration 

Calcium 

223.  Expt.  3.— Heat 

Colour  of  Beads 

a  small  quantity  of 
the  substance  in  a 

Outer 

Inner 

borax  bead  first  in 

1.  Brown, 

Olive 

Iron 

the  outer  then  in 

hot       and 

green,  hot 

the  inner  blowpipe 

yellow  cold 

and  cold 

flame 

2.  Reddish 

Colourless, 

Manganese 

purple,  hot 

hot      and 

and  cold 

cold 

If  organic  matter  is  present  the  following  additional 
tests  should  be  performed  : — 

224.  Carbon. — Heat  with  CuO  (212).  Evolution  of 
CO 2  shows  presence  of  carbon. 

225.  Chlorine. — Heat  with  lime  (215),  dissolve  in 
dilute  HNO3,  and  test  with  AgN03  solution  ;  a  white  pre- 
cipitate indicates  presence  of  chlorine. 

226.  Sulphur. — Heat  with  dilute  hydrochloric  acid 
and  KCIO3  (216)  ;  filter,  and  add  BaCl2  solution  ;  a  white 
precipitate  shows  presence  of  sulphur. 

22TJ.  Nitrogen. — If  ammonium  salts  are  absent  (221) 
heat  the  substance  with  soda-lime ;  the  evolution  of 
ammonia  gas  (213)  indicates  organic  nitrogen. 

If  ammonium  salts  are  present  heat  the  substance  with 
KHO  solution  until  ammonia  gas  ceases  to  be  evolved  ; 
filter,  mix   the    residue  with   soda-lime,  and   heat   in  an 


228-235]     WET   EXAMINATION   FOR  METALS  67 

ignition-tube  ;  evolution  of  ammonia  indicates  presence  of 
organic  nitrogen. 

WET  EXAMINATION  FOR  METALS 

228.  If  the  substance  be  a  solid  it  is  first  of  all  necessary 
to  bring  it  into  solution. 

Finely  powder  the  substance  in  a  mortar.  If  the  sub- 
stance is  very  hard  an  agate  mortar  must  be  used. 

229.  Process  of  Solution.— Boil  up  as  much  of  the 
powdered  solid  with  distilled  water  as  will  cover  a  shilling. 
If  the  substance  dissolves  proceed  with  the  analysis.  If 
some  remains  undissolved  heat  another  portion  of  the  solid 
with  dilute  hydrochloric  acid  for  several  minutes.  If  all 
dissolves  proceed  with  the  analysis.  If  all  does  not  dis- 
solve heat  a  fresh  portion  with  strong  hydrochloric  acid  to 
which  has  been  added  a  little  strong  HN03  ;  dilute,  filter 
if  necessary,  and  proceed  with  the  analysis.  If  any  residue 
is  left  it  will  require  treating  as  an  insoluble  substance  by 

paragraph  250. 

NOTES  TO  TABLE  II. 

230. — If  the  temperature  of  ignition  be  too  high,  insoluble  A120, 
and  Fe203  will  be  formed  which  will  not  redissolve  when  treated  with 
HC1.  If  organic  matter  is  present  the  dish  should  be  gently  heated 
with  a  small  flame  until  the  black  carbonaceous  matter  is  burnt  away. 

231.  —  If  AmCl  is  added  in  insufficient  quantity  Mn  and  Mg  may 
be  precipitated  with  AmHO.  If  AmCl  is  added  in  very  large  quantity 
MnS  is  prevented  from  precipitating  when  Am2S  is  added. 

232. — Since  traces  of  Mn  may  be  precipitated  with  AmHO,  it  is 
as  well  to  test  a  portion  of  this  residue  for  Mn  by  fusion  on  platinum 
foil  with  Na2C03  and  KN03,  when  a  green  mass  will  be  formed. 

233. — Since  HNOs  has  been  added  in  an  earlier  part  of  the 
analysis,  the  iron  at  this  stage  will  be  in  the  ferric  state.  A  small 
quantity  of  the  original  substance  dissolved  in  HC1  should  be  tested 
for  ferrous  and  ferric  iron  by  paragraphs  165  and  171. 

234. — Commercial  KHO  and  NaHO  frequently  contain  AL  These 
reagents  should  be  tested  by  acidulating  and  adding  AmHO. 

235.  — Potassium  may  also  be  detected  at  this  stage  by  adding  a 
small  quantity  of  strong  platinum  chloride  or  sodium  picrate  solution 
and  stirring  with  a  glass  rod ;  a  yellow  crystalline  precipitate  will  be 
formed  in  both  cases  if  K  is  present  (188,  188a). 

F  2 


68         PRACTICAL  AGRICULTURAL   CHEMISTRY      [236 

236.-TABLE   II.    FOR  THE 

Test  for  ammonium  by  heating  the  original  solid  with  KHO  solution, 
original  solution  (229)  if  not  already  acid  add  HC1  in  excess.  Add  a  few 
ignite  over  the  Bunsen  flame  (230).    Treat  with  a  little  strong  HC1,  warm, 


Residue  is 
SiO, 

This  resi- 
due should 
be  quite 
white 


The  filtrate  may  contain  Al, 
Add  a  few  drops  of  this  solution  to  some  ammonium- 
are  present ;  if  not,  phosphates  are  absent. 

To  the  rest  of  the  solution  add  Am  CI  in  moderate  quantity 
phate  is  present,  examine  this  precipitate  by  Table  III.  ;  if 
examined  as  below. 


Precipitate  may  contain  Fe2(HO)6,  Al2(HO)8  (232) 
If  the  precipitate  is  quite  white,  aluminium  only 
will  be  present ;  if  coloured,  iron  will  probably  be  present. 
Dissolve  the  residue  in  hot  dilute  HC1,  add  pure  KHO  or 
NaHO  in  excess,  then  add  more  KHO  so  as  to  have  con- 
siderable excess.     Warm  and  filter 


Residue  will  be  Fe2(OH)8 
Dissolve    in    hot  dilute 
HC1    and    add    KCNS,    a 
blood-red  coloration  shows 
Presence  of  Fe  (233) 


Filtrate  will  contain 
Al2(OH)6  dissolved  in  ex- 
cess of  KHO 

Add  strong  HC1  until 
the  solution  is  distinctly  acid, 
then  add  Am  HO  very 
cautiously  until  the  solution 
is  faintly  alkaline.  A  white 
gelatinous  precipitate  shows 

Presence  of  Al  (234) 


236]  WET  SEPARATION  OF  METALS  69 

SEPARATION  OF  THE   METALS 

ammonia  gas  will  be  evolved  which  turns  turmeric-paper  brown.  To  the 
drops  of  strong  HN03,  evaporate  to  dryness  in  a  porcelain  dish,  and  very  gently 
add  water  and  filter. 


Fe,  Mn,  Ca,  Mg,  K,  Na 

molybdate  solution  and  warm ;  if  a  yellow  precipitate  forms,  phosphates 

(231),  heat  to  boiling,  and  then  add  AmHO  in  excess ;  filter.     If  a  phos- 
absent,  examine  the  precipitate  as  below.    In  any  case  the  filtrate  must  be 


Filtrate  may  contain  Mn,  Ca,  Mg,  K,  Na 

Add  Am2S  until  the  solution  has  a  distinct  yellow  tinge.     Warm  and  filter 


Buff  precipi- 
tate     will 
beMnS 
Confirm  by 
heating        on 
platinum    foil 
with    Na2COs 
andKN03;  a 
green       mass 
shows 
Presence 
of  Mn 


Filtrate  may  contain  Ca,  Mg,  K,  Na 
Add  ammonium  oxalate  (Am2C204)  solution  in  fair 
excess,  filter 


White 

precipit  ite 

will  be 

CaC20, 

showing" 

presence 

ofCa 


Filtrate  may  contain  Mg,  K,  Na 
Evaporate  the  filtrate  to  dryness  in  a 
porcelain  dish,  scrape  out  the  residue  on  to  a 
piece  of  platinum  foil,  ignite  until  all  fumes 
cease  to  be  evolved.  Boil  the  foil  in  a  very 
small  quantity  of  water  containing  a  few 
drops  of  HC1.     Divide  into  two  portions. 


Examination 
for  Mg 
Add    AmCl, 
Am  HOin  excess, 
and     Na2HP04 
and  shake  well ; 
a  white  crystal- 
line   precipitate 
shows 
Presence  of  Mg 


Examination  for  K 

and  Na 
Take  up  a  little  of  the 
solution   on  the   loop  of 
platinum  wire  and  hold  in 
the  Bunsen  flame. 

(1)  A  pale  violet  flame 
shows 

Presence  of  K  and 
absence  of  Na 

(2)  A  bright  yellbw 
flame  shows  presence  of 
Na.  Examine  this  flame 
through  the  indigo  prism 
or  cobalt  glass  ;  a  crimson 
flame  shows 

Presence  of  K  (235) 


70  PRACTICAL  AGRICULTURAL  CHEMISTRY  [237~239a 


237.  TABLE    III.-FOR    THE   EXAMINATION    OF 
THE   PHOSPHATE   PRECIPITATE 

The  AmHO  precipitate  may  contain  FeP04)AlP04, 
Ca3P208,  MgNH4P208 

Dissolve  the  precipitate  in  hot  dilute  HC1.  To  the  solution  add 
Am^COjj  solution,  drop  by  drop,  until  the  precipitate  first  formed  re- 
dissolves  with  difficulty  (238).  Add  a  fair  quantity  of  a  mixture  of 
acetic  acid  and  ammonium  acetate  solution,  and  then  add  FeCl3  until 
the  liquid  becomes  reddish  ;  warm  and  filter. 


Filtrate  may  contain 
Ca  and  Mg- 

Add  AmHO  in  excess,  filter 
(239)  and  add  Am.2C204  solu- 
tion ;  warm  and  filter 


Precipi- 
tate will 
be  CaC,04 

showing 

presence 

of  Ca 


Filtrate  may 
contain  Mg- 
Add  Na2HP04 
solution  and 

shake ;     a     white 
crystalline  precipi- 
tate shows 
Presence  of  Mg 


Precipitate  will  contain  FeP04 
and  possibly  A1P04 

Heat  precipitate  with  K.HO  solu- 
tion ;  filter 


Filtrate  may 
contain  A1P04 
dissolved  in 
KHO 

Add  HC1  in  ex- 
cess, then  AmHO 
in  very  slight 
excess ;  a  white 
gelatinous  precipi- 
tate shows 
Presence  of Al 


Precipitate  will 
contain  FeP04, 

which  reject,  since 
iron  will  always 
be  found  at  this 
stage  owing  to 
FeCL;  having  been 
added  (239a). 


EXPLANATION   OF  THE   PHOSPHATE   TABLE 

238. — The  separation  of  the  above  phosphates  depends  on  the 
following  facts  : — 

The  phosphates  of  iron  and  aluminium  are  insoluble  in  acetic  acid, 
whereas  those  of  calcium  and  magnesium  are  soluble.  Hence  the 
HO  solution  of  the  phosphates  is  altered  by  the  addition  of  HA  and 
AmA  into  an  acetic  acid  solution,  when  A1P04  and  FeP04  precipitate. 
The  FeCL,  is  added  for  the  purpose  of  precipitating  the  remainder  (if 
any)  of  the  phosphoric  acid  as  FeP04,  and  so  leaves  the  Ca  and  Mg  as 
acetates,  which  are  then  tested  for  by  the  usual  reagents. 

239. — It  is  usually  necessary  to  filter  at  this  stage,  since  a  little 
iron  may  be  left  in  the  solution.  The  AmOH  would  then  cause  a 
brown  precipitate,  which  is  neglected. 

239a. — This  precipitate  of  FeP04  is  neglected  here,  since  FeCL,  has 
been  added.  Iron  should  be  tested  for  in  the  original  solution  by 
tests  (165  and  171).     It  should  be  noted  that  the  metals  Ca  and  Mg 


240-245]       EXAMINATION   FOR   ACID-RADICALS 


may  also  be  present  '  not  as  phosphate,'  and  of  course  will  be  found  in 
Table  II. 

The  four  metals,   Fe,   Al,   Ca,  and   Mg,  should  be  returned  'as 
phosphate  '  or  •  not  as  phosphate,'  exactly  as  they  are  found. 


TABLE  IV.— PRELIMINARY   EXAMINATION 
FOR  ACID-RADICALS 

In  the  following  tests  either  the  solid  or  a  strong-  solution  may  be 
used : — 


Test 

Observation 

Inference 

240.  Expt.  I.— Treat 
a  little  of  the  substance 
with   dilute    HC1    and 
heat  gently 

1.  A  colourless  gas  is 
given    off  which   turns 
lime-water  milky 

2.  Red  fumes 

CO.j  from  a 
carbonate 

N.,03  from  a 
nitrite 

241.  Expt.  II.— Heat 
a  little  of  the  substance 
with  strong  H2S04 

242. — Confirm  by  heat- 
ing   another    portion    with 
Mn02,   free  from  chloride, 
and  strong  sulphuric  acid 

243.  —  Confirm  by  drop- 
ping a  few  Cu  turnings  into 
the  liquid  and  heat  again 

1.  A  gas  with  a  pun- 
gent acid  smell  is  given 
off  which  fumes  in  the 
air  and  turns  a  drop  of 
silver    nitrate  solution 
milky 

A  pale  yellow  gas  is  given 
off  with  choking  smell,  and 
which  bleaches  test-papers 

2.  An    acid    gas    is 
given   off,   occasionally 
reddish  in  colour 

Red  fumes  given  off 

HC1  from  a 
chloride 

CI       from      a 
chloride 

Presence  of 
a  nitrate 

NO     from     a 
nitrate 

TABLE  V.— FURTHER  EXAMINATION  FOR  ACID- 
RADICALS 

244.  Sulphate.— Boil  a  little  of  the  original  substance 
with  dilute  HC1,  filter,  and  add  barium  chloride  solution  ; 
a  white  precipitate  of  BaS04  shows  presence  of  a  sulphate. 

245.  Chloride.— Boil  a  portion  of  the  original  sub- 
stance with  dilute  fiN03,  filter,  and  add  AgN03  solution; 
a  white  precipitate  denotes  presence  of  a  chloride. 


72   PRACTICAL  AGRICULTURAL   CHEMISTRY    L'246-251 

246.  Nitrite. — Boil  with  water,  filter,  and  test  with  Kl 
solution,  starch,  and  HA  (197)  ;  a  blue  coloration  will 
appear. 

247.  Nitrate. — Boil  the  original  substance  with  water  ; 
filter,  cool  under  the  tap,  and  add  very  cautiously  an  equal 
bulk  of  strong  sulphuric  acid  ;  cool  in  water.  When  quite 
cold  add  slowly  down  the  sides  of  the  tube  a  little  of  a  cold 
solution  of  FeS04.  Where  the  liquids  come  in  contact  a 
brown  ring  will  be  formed. 

248.  Phosphate. — A  phosphate,  if  present,  will 
usually  have  been  detected  in  Table  II.  (236).  It  is  readily 
detected  by  boiling  the  original  substance  with  dilute 
HNO3  and  then  adding  a  few  drops  of  this  solution  to 
ammonium  molybdate  solution  ;  a  yellow  precipitate  forms 
on  warming. 

249.  Silicate. — A  silicate  will  usually  be  found  in 
Table  II.  (236).  It  may  be  readily  detected  if  a  little  of  the 
finely  powdered  substance  is  fused  with  Na2C03  on  plati- 
num foil,  and  then  treated  with  HC1.  On  evaporating  to 
dryness  the  Si02  will  be  rendered  insoluble,  so  that  on 
treating  with  HC1  and  water  the  Si02  will  be  left  as  a  white 
powder  (208). 

ANALYSIS  OF  SUBSTANCES   INSOLUBLE   IN 
WATER  AND  ACIDS 

250.  The  insoluble  substances  usually  associated  with 
agricultural  products  are  silica,  silicates,  and  phosphates. 

251.  Mix  the  finely  powdered  substance  with  six  times 
its  weight  of  fusion  mixture  (268).  Place  in  a  porcelain 
or,  preferably,  a  platinum  crucible.  Heat  gently  at  first, 
then  strongly  over  the  blowpipe.  Continue  the  heating  until 
all  effervescence  ceases.  Allow  to  cool  and  place  the 
crucible  and  contents  in  a  beaker,  and  gently  heat  with 
dilute  HC1  until  the  residue  is  all  dissolved,  or  only  gelati- 


252-258]  INSOLUBLE   SUBSTANCES  J I 

nous  silica  is  left.  Transfer  to  a  porcelain  dish,  cautiously 
evaporate  to  dryness,  and  ignite  gently.  Now  cover  with 
strong  HC1,  warm,  and  dilute  with  water.  The  silica  will  be 
left  in  an  insoluble  form,  and  may  be  filtered  off. 

252.  The  solution  is  then  examined  for  metals  by 
Tables  II.  and  III.  (236  and  237),  and  for  acid-radicals  by 
Tables  IV.  and  V.  (240-249). 

253.  Since  HC1  has  been  added,  a  portion  of  the  original 
powder  should  be  boiled  with  sodium  carbonate  solution, 
the  solution  filtered,  and  then  tested  for  chloride  by  adding 
dilute  HNO3  m  excess,  and  afterwards  AgN03  solution, 
when  a  white  precipitate  of  silver  chloride  will  form  if 
chloride  is  present. 

254.  Nitrates  are  not  found  in  insoluble  bodies,  as  all 
nitrates  are  soluble  in  water. 

255.  Since  Na  and  K  cannot  be  tested  for  in  the  solu- 
tion obtained  after  fusion,  owing  to  the  fusion  mixture 
consisting  of  Na2C03  and  K2C03,  it  is  necessary  to  use  a 
separate  portion  for  the  detection  of  these  metals. 

256.  The  most  convenient  method  is  that  of  Lawrence 
Smith.  Mix  the  powdered  substance  with  six  times  its 
weight  of  a  mixture  of  one  part  pure  solid  AmCl  and  six  parts 
pure  precipitated  CaC03.  Place  in  a  crucible,  and  heat  to 
redness  for  twenty  minutes.  Allow  to  cool,  boil  up  with 
water,  and  filter.  The  filtrate  will  contain  the  alkalies 
together  with  excess  of  calcium  hydroxide.  Precipitate  the 
calcium  by  adding  AmHO,  Am2C03,  and  a  few  drops  of 
Am2C20,  solution ;  filter,  evaporate  to  dryness,  and 
ignite. 

257.  Dissolve  in  a  very  small  quantity  of  water ;  test 
for  sodium  by  holding  a  little  of  the  solution  in  the  Bunsen 
flame  on  a  platinum  wire,  when  the  golden  flame  coloration 
will  be  seen  if  Na  is  present. 

258.  Potassium  may  be  detected  by  viewing  the  flame 
through  an  indigo  prism  or  cobalt  glass,  when  the  crimson 


74       PRACTICAL  AGRICULTURAL   CHEMISTRY         [259 

coloration  will  be  seen  if  K  is  present.  Potassium  may 
also  be  detected  by  platinum  chloride  (188)  or  sodium 
picrate  (188a). 

259.— Example  of  Method  of  Entering  the  Results  op 
an  Analysis  in  the  Note-book 

Examination  of  pale  brown  earthy  substance 

Preliminary  Examination  for  Metals 


Experiment 

Observation 

Inference 

I.  Heated  in  an  ig- 
nition-tube 

Little  water  given 
off;  no  charring 

H20  present,  or- 
ganic matter  absent 

2.  Heated  on  Pt  wire 
in   Bunsen   flame  after 
moistening  with  HC1 

Yellowish    -    red 
flame 

Trace  Na ;  Ca 
present 

3.  Heated   in   borax 
bead 

No  result 

Fe,  Mn  probably 
absent 

Wet  Examination 

Boiled  substance  with  water ;  did  not  dissolve.  Treated  with 
dilute  HC1,  all  dissolved.  Evaporated  to  dryness,  moistened  with 
HC1,  added  water,  filtered  off  trace  of  SiOi}  and  tested  filtrate  for 
metals. 

Heated  a  few  drops  of  solution  with  ammonium  molybdate,  obtained 
no  precipitate  ;  hence  phosphates  were  absent.  To  bulk  of  solution 
added  AmCl  and  AmHO. 


No  pre- 
cipitate ; 

.*.  Fe 
and  Al 

absent 


To  solution  added  Am2C20o  filt  ered 


White  pre- 
cipitate 
Ca  present 


Evaporated  to  dryness,  ignited,  dissolved 
residue  in  dilute  HC1,  divided  into  two 
portions 


1.  Added  AmHO 

and        Na,HP04, 

white      crystalline 

precipitate 

Mg  present 


2.  Tested  on  Pt  wire 
in   Bunsen  flame,  faint 
yellow  flame,  no  crimson 
colour  through  prism 
,\  Trace  Na  present 


259]  METHOD  OF   ENTERING   RESULTS 

Preliminary  Examination  for  Acid-radicals 


75 


I.   Heated    with 

Gas  given    off   with 

Presence  of  car- 

dilute HC1 

effervescence,       which 
turned          lime  -  water 

bonate 

milky ;    no   red   fumes 

Nitrite  absent 

evolved 

2.  Heated   with 

Ditto 

Probable  absence 

strong  H2S04 

of     chloride    and 
nitrate 

Wet  Examination  for  Acid-radicals 


1.  Heated  substance  with 
dilute  HC1,  filtered,  added 
BaCl2  and  warmed 

2.  Heated  substance  with 
dilute  HNO:„  filtered,  and 
added  AgN03 

3.  Heated  substance  with 
water,  filtered,  added  strong 
HJ304,  cooled,  and  then 
added  cold  FeS04  solution 


Faint      white 
precipitate 

Faint     milki- 
ness 


No  brown  ring 


Trace  of  sul- 
phate 


Trace 

chloride 


of 


Nitrate  absent 


Phosphate  was  shown  to  be  absent  in  the  wet  examination  for  the 
metals. 

Found :  Ca,  Mg-,  water,  carbonate,  traces  of  sodium, 
chloride,  silicate,  and  sulphate 


76         PRACTICAL  AGRICULTURAL  CHEMISTRY      [260 


SECTION   V 

APPARATUS,    CHEMICALS  AND  REAGENTS 
List  of  Bench  Apparatus  for  each  Student 

200.  A  list  of  the  apparatus  which  should  be  kept  in 
each  bench-locker  is  given  here.  The  Bunsen  burner,  with 
its  indiarubber  tube,  may  be  left  attached  to  the  gas-tap  on 
the  bench.  All  the  other  apparatus  should  be  locked  up 
in  the  bench-locker  when  not  in  use. 

1  Bunsen  burner  about  5 \  inches  high,  with  |-inch 
tube,  and  means  of  closing  the  air-holes. 

1  Rose-top  to  fit  burner. 

1  Piece  of  black  indiarubber  tubing,  -^  inch  internal 
diameter  and  16  inches  long,  to  supply  gas  to  the  burner. 

1  Test-tube  stand  with  twelve  holes,  two  of  which  are  at 
least  an  inch  across. 

1  Test-tube  brush. 

1 2  Test-tubes,  5  inches  long  by  f  inch  diameter. 

2  Boiling-tubes,  6  inches  long  by  1  inch  diameter. 

2  Round  glass  plates,  ground  on  one  side,  3  inches  across. 
2  Berlin  porcelain  evaporating-dishes  with  spouts,  glazed 
inside  and  out,  and  3  inches  in  diameter. 

2  Watch-glasses,  2  inches  across. 
Conical  flask,  4  oz.  capacity. 

1  Wedgwood  mortar,  4  inches  across,  and  pestle  with 
wooden  handle. 

1  Iron  tripod  stand,  7  inches  high,  with  round  top 
4  inches  across. 

1  Piece  of  coarse  iron  wire  gauze,  5  inches  square. 

3  Glass  funnels,  two  of  them  2J  inches  across,  one 
2  inches  across. 


261]  APPARATUS  FOR  GENERAL  USE 


77 


3  Beakers,  wide  form  of  2,  4,  and  6  oz.  capacity. 

3  Glass  rods,  rounded  at  the  ends,  7,  6,  and  3  inches 
in  length. 

1  Piece  of  platinum  foil,  1  x  i^  inch. 

2  Pieces  of  platinum  wire,  mounted  (7). 
1  Black's  blowpipe,  japanned  tin. 

1  Pipe-clay  triangle,  2  inches  along  the  side. 
1  Wash  bottle,  to  be  made  from  18  oz.  flask  (10). 
1  Retort  stand.    Upright  rod  17  inches,  foot  6x3  inches, 
with  three  brass  rings,  the  largest  3  inches  across. 

1  Wooden  filter-stand,  1 2  inches  high,  with  two  rings. 
1  Pair  polished  brass  crucible  tongs,  6  inches  long. 
1  Small  horn  spatula,  3J  inches  long. 
1  Oval  wicker  draining  basket,  10x8x4  inches. 
Cut  filter-papers,  4^,  3 J,  and  2|  inches  across. 
1  White  porcelain  tile,  4^  inches  square. 

List  of  Special  Aparatus  for  Sections  I.,  II.,  and  III. 

261.   This    apparatus  need  not  be  supplied  to  each 
student,  but  several  sets  should  be  kept 

1  Nest  of  three  or  four  small  brass  cork-borers. 

1  Triangular  file. 

1  Thin  round  file. 
Several  lengths  and  pieces  of  hard  glass-tubing,  about 
£  inch  internal  diameter. 

1  Gross  ignition-tubes,  3  inches  long,  J  inch  across. 

1  Gross  corks,  as  free  as  possible  from  holes  or  cracks, 
varying  from  §  to  j  inch  across. 

1  Small  metal  clamp  in  a  boss  .fitting  the  retort  stand 

(%  15)- 

i  Stoppered  bell-jar,  30  oz.  capacity. 

4  Glass   cylinders  on  feet  with  ground  edge  at  top, 
8  inches  high,  if  inch  across. 

4  Similar  cylinders,  6  inches  high,  i\  inch  across. 


78  PRACTICAL  AGRICULTURAL  CHEMISTRY  [262 

i  Round  brown  stoneware  trough,  12  inches  across, 
5  inches  deep. 

1  Metal  deflagrating-spoon. 

2  Two-necked  Woulffe's  bottles,  8  oz.  capacity. 

1  Tubulated  retort,  6  oz.  capacity. 

2  Thistle  funnels,  8  inches  long. 

4  Pieces  of  black  indiarubber  tubing,  ^  inch  in  internal 
diameter,  1^  inch  long. 
Wooden  spills. 
Wax  tapers. 
1  Pair  of  scissors. 
1  Brass  wire  sieve,  20  meshes  to  the  inch. 

List  of  Apparatus  for  General  Use  in  Analysis 

262:  The  following  apparatus  should  be  kept  in  the 
laboratory  for  the  general  use  of  students.  One  set  will 
suffice  for  about  twelve  students. 

1  Spirit-lamp,  4  oz.  capacity,  with  earthenware  wick- 
holder  and  ground  glass  cap. 

If  gas  is  not  available  a  set  of  these  lamps  will  be  required  in  place 
of  Bunsen  burners  (260). 

4  Berlin  porcelain  crucibles,  1  \  inch  across,  with  covers. 

1  Iron  mortar,  8  inches  across,  with  pestle. 

1  Fletcher's  foot-bellows  and  blowpipe- table  covered 
with  sheet  zinc  or  lead. 

1  Fletcher's  blowpipe  with  central  blast  and  2  taps. 

1  Indigo  prism,  stoppered,  nearly  filled  with  solution  of 
indigo  in  strong  sulphuric  acid.  The  indigo  solution  is 
made  by  mixing  commercial  sulphindigotic  acid  with  ten 
times  its  measure  of  strong  sulphuric  acid,  leaving  to  settle 
for  several  days  and  decanting  into  the  prism. 

N.B. — Cobalt-blue  glass  may  be  substituted  for  the 
above. 

1  Agate  mortar,  3  inches  across,  and  pestle. 

1  Copper  water-bath,  with  several  openings  (fig.  11). 
When  in  use  it  should  be  two-thirds  filled  with  water,  and 


263] 


CHEMICALS  AND  REAGENTS 


79 


more  water  added  from  time  to  time  to  make  up  for  evapo- 
ration, or  preferably  the  bath  is  fitted  with  a  constant  level 
water-supply. 

i  steam- oven   (fig.    14)  made   of  copper.     The  water 
should  two-thirds  fill  the  oven,  and  should  be  kept  just 
below  boiling.     The  loss  by  evaporation  should  be  made 
good  from  time  to  time,  if  not  fitted  as  described  above. 
CHEMICALS  AND  REAGENTS 

263.  In  the  following  lists  will  be  found  the  reagents 
and  test  substances  required  in  the  course.  In  the  first 
column  stands  the  name ;  in  the  second  the  chemical 
formula  of  the  substance.  The  subsequent  columns  give 
directions  for  their  preparation  for  laboratory  use. 

264.— Reagents  required  for  each  Bench 


Name 


Formula 


Weight  of  solid 

in  grams  to  be 

dissolved  in  one 

Winchester  of 

water 

(2,500  c.c.) 


Sulphuric  acid  .... 
Hydrochloric  acid      .     . 

Nitric  acid 

Acetic  acid 

Ammonium  chloride  .  . 
Ammonium  hydrate  .  . 
Ammonium  sulphide  .  . 
Ammonium       carbonate 

{note  1) 

Ammonium  oxalate  .  . 
Potassium  hydrate  .  . 
Potassium  ferrocyanide  . 
Potassium  ferricyanide  . 
Sodium  phosphate 
Sodium  carbonate 
Calcium  sulphate  . 

Barium  chloride     . 
Sodium  carbonate 

Borax 

Potassium  chlorate 
Test-papers  .     .     . 


H2S04  .  .  . 
HC1  .  .  .  . 
HNO3  .... 
HC2H302  or  HA 
NH4C1  .  .  . 
NH4HO  .  . 
(NH4)2S  .  . 
(NH4)2C03      . 

(NH4)2C204.H20, 
KHO  .  .  . 
K4Fe(CN)6.3H20, 
K3Fe(CNJ6(»*/*2) 
Na2HP04.i2H20 
Na2C03.ioH20  . 
CaS04    .     .     .     . 

BaCl2.2H20  .  . 
Na2C03  •  •  . 
Na2B407.ioH20  . 
KCIO5    .     .     .     . 


300 


400 

100 
300 
200 
200 
200 
600 
Saturated   so- 
lution 
200 
Solid 
Solid 
Solid 
Blue  and  red  lit- 
mus and  yellow 
turmeric-papers 
in  small  strips 


3m 
3m 
1  m 
8w 
3m 
1  m 
6  w 

24  w 

8  w 

12  w 

12  w 

12  W 

4W 


80        PRACTICAL  AGRICULTURAL  CHEMISTRY       [265 


Note  i. — The  solid  (NH,)zC0M  is  dissolved  in  cold  water,  but  in 
diluting,  one-fourth  of  the  *  Winchester'  must  be  filled  with  3trong 
NH4HO. 

Note  2.— This  reagent  undergoes  decomposition  by  exposure  to 
light,  and  must  not  be  kept  near  a  window :  it  is  better  to  dissolve  a 
fragment  of  the  solid  each  time  it  is  required. 

265.— Chemicals  required  for  Sections  I.  and  II. 

With  the  exception  of  the  bench  reagents  the  whole  of  the  sub- 
stances required  for  these  sections  are  enumerated  below  : — 


Name 

Formula 

Remarks 

Alum  ..... 

A1K(S04)2.I2H.20 

Solid 

Ammonium  chloride     . 

NH4C1       . 

Solid 

Calcium  chloride           . 

CaCl2 

Solid  and  solution 

Manganese  sulphate     . 

MnS04       . 

Solid 

Potassium  nitrate 

KNO, 

Solid 

|  Marble         .... 

CaCO, 

In  lumps 

Manganese  dioxide 

Mn02 

Solid 

Wood  charcoal     .         . 

C       . 

In  pieces  the  size 
of  a  hazel-nut 

Lime-water          •        •        . 

Ca(OH)2    . 

Saturated  solution 

Sulphur       .... 

S       . 

Pieces  of  roll  sul- 
phur the  size  of 
a  pea 

Phosphorus          .         . 

P       . 

Kept  under  water 

Granulated  zinc   .         . 

Zn     .         .         . 

Not      necessarily 

Hydrochloric  acid 

i;ci . 

pure 
Strong 

Sulphuric  acid 

HvS04       . 

Strong 

Nitric  acid  .... 

HN03     . 

Strong 

Potassium  iodide.         . 

KI    . 

Solid 

Starch  powder     .         .         . 



_ 

Slaked  lime 

Ca(OH)2    . 

Solid 

Ammonia    .... 

NH4(OH)  . 

Strong  solution 

AgNOs      . 

Solution 

Methylated  spirit 

C2H60       .        . 

Free  from  coal-oil 

Mercuric  chloride         .         . 

HgCl2        .        . 

Solid 

Potassium  hydrate 

KHO 

Solid 

Nessler's  Solution  {note  1)    . 

— 

— 

Note  1. — Dissolve  33  grams  of  KI  and  13  grams  of  HgCl2  in 
800  c.c.  of  water,  add  strong  HgCl2  solution  antil  a  faint  permanent 
precipitate  is  formed,  then  add  160  grams  of  solid  KHO.  Allow  to 
cool  and  make  up  to  one  litre  with  water.  Use  the  clow  supernatant 
liquid. 


266.— Substances 

used  for  Section 

III. 

Name 

Formula 

Remarks 

Loam    ..... 



Air-dried 

Lime-water   . 

Ca(OH)2    . 

Saturated 

solution 

Clay 

— 

Air-dried 

Marble  ..... 

CaC03      . 

Ground  fine 

Peat  soil        .... 

— 

Air-dried 

Quicklime      . 

CaO 

Freshly  burned 

Litmus  solution 

— 

— 

Ferrous  sulphate    . 

FeS04.7H20     . 

Solid 

— 

Fresh 

Gypsum         .... 

CaS04.2HaO     . 

Solid 

Charcoal        .... 

C 

Powder 

Kainit 

K1Mg(S04)r6H10 

Commercial 

Coprolite  powder   . 

— 

— 

Basic  slag       .... 

— 

— 

CaH4(P04)2       . 

Commercial 

Citrate  of  ammonium  (note  i) . 

(NH4)SCI  . 

Solution 

(NH4)2S04        . 

Commercial 

Nitrate  of  soda 

NaNOs     . 

Commercial 

Shoddy 

— 

— 

Soda-lime      .... 

— 

Granulated 

Indigo  carmine 

— 

Solution 

Sulphuric  acid 

H2S04      . 

Strong 

Peruvian  guano 

— 

— 

Ammonium  molybdate  (note  2) 

NH4HMo04     . 

Solution 

Ferric  chloride 

FeCl3        . 

Solution(i:ioo) 

Potassium  sulphocyanide 

KC.NS      . 

Solution(i:ioo) 

Bone-meal      .... 

— 

— 

Linseed  cake 

— 

Ground  fine 

Cotton  cake,  decorticated 

— 

Ground  fine 

Cotton  cake,  undecorticated    . 

— 

Ground  fine 

Glycerine       .... 

C3Hs(OH)3        . 

— 

Ether 

C4Hl0O     .         . 

— 

— 

— 

Solution  of  iodine  in  potassium 

iodide 

I  and  KI  . 

Dilute  solution 

Alcohol  (methylated  spirit)     . 

C2H80      . 

Free  from  coal- 
oil 

Hay       .         .         .         . 



Turnips          .... 

— 

Provided  fresh 
when  wanted 

Cane  sugar     .... 

— 

Crystallised 

Glucose          .... 

— 

— 

Carbolic  acid 

— 

80  %  solution 

Formalin        .... 

CH20       . 

40  %  solution 

Flour    

— 

Wheaten 

Milk 

— 

Fresh 

Butter 

— 

Fresh 

Cheese 

— 

Fresh 

82         PRACTICAL  AGRICULTURAL  CHEMISTRY      [267 

Note  |, — Made  by  rendering  a  strong  solution  of  citric  acid  dis- 
tinctly alkaline  with  ammonia. 

Note  2.— Measure  ioo  c.c.  water  into  a  large  flask,  add  50  grams 
molybdic  acid  or  70  grams  of  ammonium  molybdate,  then  100  c.c.  of 
strong  ammonia  ;  stir  until  dissolved.  Pour  the  solution  into  720  c.c 
cold  nitric  acid,  sp.  g.  1  "20,  stirring  whilst  adding. 

Note  3.— Best  kept  as  two  solutions,  A  and  B  :  A  contains  about 
35  grams  of  copper  sulphate  dissolved  in  500  c.c.  of  water,  B  contains 
173  grams  of  Rochelle  salt  (sodium  potassium  tartrate)  and  160  grams' 
of  potassium  hydrate  in  500  c.c.  of  water.  For  immediate  use  equal 
quantities  of  each  are  mixed. 


267.— Reagents  for  General  Use  for  the  Detection 
of  Metals 


Name 

Formula 

Proportion  by  weight  of 
solid  to  water 

Sulphuric  acid 

H2S04  . 

Strong  pure 

Hydrochloric  acid  . 

HC1      . 

Strong  pure 

Nitric  acid 

HN03  . 

Strong  pure 

Platinum  chloride    . 

PtCl4    . 

1  :  3° 

Methylated  spirit     . 

C2HuO  .        . 

Strong 

Slaked  lime    . 

Ca(HO)2 

Solid 

Potassium  sulphocyanide. 

KCNS  . 

1  :  100 

Potassium  nitrate    . 

KNOs  . 

Solid 

Silver  nitrate  . 

AgN03 

1  :  100 

Magnesium  sulphate 

MgS04.7H20 

1  :  12 

208]         REAGENTS   FOR  THE  ACID-RADICALS 


83 


J. — Reagents  for  General  Use  for  the  Detection  of 
Acid-radicals 


Proportion        by 

Name 

Formula 

weight  of  solid  to 
water 

Lime-water        .         .         . 

Ca(OH)2       . 

Saturated 

Ferric  chloride  {note  1) 

FeCL,  .         .         . 

1  :  24 

*Ferrous  sulphate 

FeS04.7H,0 

Solid 

Potassium  iodide 

KI       .      "  . 

1  :  60 

*Starch      .... 

— 

— 

Indigo  carmine  solution 

— 

— 

Manganese  dioxide  {note  2). 

MnO.,  . 

Solid 

Ether  (methylated)     . 

— 

— 

*  Potassium  nitrite 

KN02 . 

Solid 

Ammonium  molybdate  {n.  3) 

NH4HMo04 

— 

Microcosmic  salt 

NaNH4HP04.4H,0 

Solid 

Wax  or  paraffin . 

— 

Solid 

Distilled  water  . 

H20    . 

— 

Pure  sodium  hydrate  . 

NaHO 

1  :  10 

Fusion  mixture  {note  4) 

K2C03  +  Na2C03 . 

— 

Solution  of  sodium  acetate  in 

dilute  acetic  acid  {note  5). 

NaA  and  HA       . 

— 

Calcium  carbonate,  pure 

CaC03. 

Powder 

Ammonium  chloride,  pure  . 

NH4C1 

Powder 

*Potassium  ferricyanide 

K3Fe(CN)6  . 

Solid 

*  These  solids  do  not  keep  in  solution. 

Note  1. — The  solution  should  not  contain  any  free  acid.  To  remove 
this  AmHO  is  added  until  the  further  addition  of  a  single  drop  gives 
a  reddish-brown  precipitate.  Filter  off  this  precipitate,  and  the  solu- 
tion is  ready  for  use. 

Note  2. — Should  be  kept  in  fine  powder ;  it  must  not  evolve  CI  or 
C02  when  warmed  with  strong  H2S04. 

Note  3. — See  note  2,  paragraph  266. 

N0te  4.— Dry  finely  powdered  Na2COa  and  K2COs  are  mixed  in 
proportions  of  53  :  69  by  weight  and  kept  in  a  stoppered  bottle. 

Mote  5.— Dissolve  20  grams  NaA  in  60  c.c.  of  distilled  water  and 
add  to  the  solution  40  c.c.of  strong  HA. 


84   PRACTICAL  AGRICULTURAL  CHEMISTRY   [269-270 


269.— Solutions 

for  the  Reactions  of  the  Metal3 

Name 

Formula 

Weight  of  solid 

in  grams  to  be 

dissolved  in  one 

Winchester  of 

water 

Proportion 

by  weight 

of  solid  to 

water 

Potassium  chloride     . 

KC1     . 

100 

1:25 

Ammonium  chloride  . 

NH4C1 

200 

1  :  12 

Sodium  chloride 

NaCl  . 

So 

1:50 

Magnesium  sulphate  . 

MgS04.7H2O     . 

So 

i:5o 

Calcium  chloride 

CaCl2.6H20 

200  (in  crystals) 

1  :  12 

Alum. 

A1K(S04)2  .  i2H20 

200 

1  :  12 

Ferric  chloride  . 

FeCl,         .       . 

25 

1  :  100 

Ferrous  sulphate 

FeS04.7H20       . 

25 

1  :  100 

Manganese  sulphate  . 

MnS04 

25 

1  :  100 

27a. —Solutions  for  the  Reactions  of  the  Acid-radicals 


Name 

Formula 

1 

Weight  of  solid 

in  grams  to  be 

dissolved  in  one 

Winchester  of 

water 

Proportion 

by  weight 

of  solid  to 

water 

Sodium  sulphate 
Sodium  carbonate 
Potassium  nitrite 
Potassium  nitrate 
Sodium  chloride 
Sodium  phosphate 
Sodium  silicate  . 
Silica  (white  sand)      . 

Na2S04.ioH20  . 
Na2C03      . 
KN02 

KN03         .        . 
NaCl  . 

Na2HP04.i2H20 
Na-jSiOs      . 
Si02    . 

25 

100 
IOO 

50 

50 

IOO 

1  :  100 
Solid 
1:25 
1:25 

1:50 
1:50 
1:25 
Solid 

Note. — The  above  substances  (269,  270)  will  also  be  required  in 
the  solid  form  for  many  of  the  tests. 


271-272]       ATOMIC   WEIGHTS  OF   ELEMENTS 


85 


271.— List  of  Chemical  Elements,  with  their  Symbols 
and  Atomic  Weights 

The  words  in  brackets  are  the  Latin  names  of  the  elements  from 
which  the  symbols  have  been  derived. 


Name 

Symbol 

Atomic 
Weight 

Name 

Symbol 

Atomic 
Weight 

Aluminium 

Al 

27 

Molybdenum    . 

Mo 

96 

Antimony  (stibium)  . 

Sb 

120 

Nickel 

Ni 

59 

Arsenic 

As 

75 

Niobium    .        . 

Nb 

94 

Barium 

Ba 

i37'4 

Nitrogen  . 

N 

M 

Beryllium 

Be 

9 

Osmium    .        . 

Os 

191 

Bismuth 

Bi 

208 

Oxygen      .         .        . 

O 

16 

Boron 

B 

11 

Palladium 

Pd 

107      " 

Bromine 

Br 

80 

Phosphorus 

P 

31 

Cadmium 

Cd 

112-4 

Platinum   . 

Pt 

*95 

Caesium 

Cs 

133 

Potassium  (kalium)  . 

K 

39 

Calcium 

Ca 

40 

Rhodium  . 

kh 

103 

Carbon 

C 

12 

Rubidium .         .         . 

Rb 

85'5 

Cerium 

Ce 

140 

Ruthenium        . 

Ku 

i'  2 

Chlorine 

CI 

35'5 

Selenion     .         . 

Se 

79 

Chromium 

Cr 

52 

Silicon 

Si 

28*4 

Cobalt 

Co 

59 

Silver  (argentum) 

Ag 

108 

Copper  (cuprurr 

)       ! 

Cu 

63-5 

Sodium  (natrium) 

Na 

23 

Didymium 

D 

142 

Strontium . 

br 

8?'5 

Erbium 

E 

166 

Sulphur      . 

S 

32 

Fluorine    . 

F 

19 

Tantalum .        * 

Ta 

181     ". 

Gold  (aura  in) 

Au 

197 

Tellurion  . 

Te 

127*6 

Hydrogen 

H 

i'oi 

Thallium   .         . 

Tl 

204 

Indium 

In 

"3"4 

Thorinum  . 

Th 

232-5 

Iodine 

I 

127 

Tin  (stannum)  . 

Sn 

119 

Iridium 

Ir 

J93 

Titanium  . 

Ti 

48 

Iron  (ferrum) 

Fe 

56 

Tung>ten    (wolfra-\ 
mium)     .         .       / 

W 

I8| 

Lanthanum 

la 

138 

Lead  (plumbum 

)     ! 

Pb 

207 

Uranium   . 

U 

238*5 

Lithium     . 

L 

7 

Vanadium .        .        . 

V 

5i 

Magnesium 

Mg 

24  "4 

Yttrium     . 

Y 

89 

Manganese 

Mn 

55 

Zinc  .... 

Zn 

65-4  , 

Mercury    (hydrar-  \ 
gyrum)  .        .       / 

Hg 

200 

Zirconium . 

Zr 

9i 

272.— Thermometric  Scales 

There  are  two  different  thermometric  scales  in  use  in  this  country, 
the  Centigrade  and  Fahrenheit ;  the  former  of  these  is  rapidly  becom- 
ing universal  for  scientific  purposes.  The  two  scales  are  mutually 
convertible  by  the  following  formake,  in  which  F.°  represents  a  tem- 
perature on  the  Fahrenheit  scale,  C.°  a  temperature  on  the  Centigrade 
scale  : — 

I  (F.°  -  32)  =  C.° 

I   C.°  +  32    -  F.° 

The  temperatures  occasionally  referred  to  in  this  book  are  given  on 
the  Centigrade  scale. 

G3 


8(5    PRACTICAL  AGRICULTURAL  CHEMISTRY  [273-274 


273. — English  Weights  and  Measures 

apothecaries'  weight  avoirdupois  weight 


lb.        oz.        drnis.         scruples  grains 

1  =    12     =  96      =       288       =  5760 

1     =     8      =       .24      =  480 

I      =          3       =  60 

1       =  20 


lb. 


07.. 

drms. 

grains 

l6 

=       256     = 

7000 

I 

*         16     = 

437'5 

z     = 

27*341 

gallon 


IMPERIAL    MEASURE 


pints 

fluid  oz. 

fluid  drms. 

8 

s= 

160 

■ 

1280 

1 

= 

20 

■i 

160 

1 

SB 

8 

1  gallon 

1  fluid  ounce  =  V5  pint 

x  gallon 

z  fluid  ounce 


70,000  grains  of  water  at  i6*7°C 

437'50  lUl       I.  " 

277  280  cubic  inches 
i"733  m 


274.— Metric  Weights  and  Measures 


MEA 

SURES  OF   LEN( 

;th 

ENGLISH 

metre 

inches 

mile 

furlong 

Millimetre     = 

o'ooi  = 

o*o3937  = 

Centimetre    = 

o'oi    = 

0*39371  = 

t 

Decimetre     = 

o'i      = 

3-93708  = 

# 

Metre             = 
Decametre    = 

x*o      = 
xo'o      = 

39'37079  = 
393-70790  = 

• 

• 

Hectometre  = 

1000      = 

3937'o79oo  = 

# 

t 

Kilometre      = 
Myriometre  = 

IOO^'O        *= 

3937o  79000  = 

. 

4 

lOOCO'O        = 

393707'9oo-.o  = 

6 

z  inch  =  '0254  metre. 

z  foot  =  '3048 

»» 

inches 


. 

. 

0*03937 

• 

• 

C3937  z 

• 

• 

3'937i 

• 

3 

3'37i 

10 

a 

9*7 

109 

T 

1 

213 

4 

io'a 

156 

0 

6 

MEASURES  OF   CAPACITY 
I  litre  =  1  cubic  decimetre 


1  Millilitre,  or  I 
I     Cubic  centimetre  (c.c.)  J 

Centilitre  = 

Decilitre  as 

Litre  c= 

Decalitre  = 

Hectolitre  = 

Kilolitre  s* 

Myiiolitm  = 


litre 


0001 


001 

o'i 

i*o 

io'o 

zoo'o 

iooo'o 

ioooo'o 

f  cubic  inch  = 
f  cubic  foot  = 
1  gallon  m 


cubic  inches 
m  0*06103 

=  0*61027 

=  6"zo27 

=  61*027 

=         610*27 
a=         6102 '7 
=     6 1027 'o 
=   610270*0 
0*01639  litre. 
28*3T53i  litres. 
4*S4336       „ 


pints 

0*00176 

0*01761 

0*17608 

1*76077 

1760773 

176*07734 

I76o-7734i 

17607*73414 


274] 


DECIMAL  WEIGHTS 


87 


MEASURES  OF   WEIGHT 


gi  am  =  the  weight  of  i  cubic  centimetre  (c.c.)  of  water  at  40  C. 


grammes 

grains 

Avoirdupois 

Milligram 

=              o'ooi 

-- 

0*01543 

Centigram 

=              o'ot 

= 

0-15432 

Decigram 

=                    O'l 

= 

i*54323 

Gram 

=                     I'O 

= 

I5'43235 

lb.      oz.     drms. 

Decagram 

=             100 

= 

154*32340 

=      00        565 

Hectogram 

=           ioo'o 

= 

154  J*23488 

=      03        8-5 

Kilogram 

=         iooo"o 

— 

-     15432*34880 

=      235 

Myriogram 

=          IOOOO'O 

= 

i54323'488oo 

=      22        I           9 

1  grain 

- 

0*0649  gram. 

x  oz.  (Troy) 

- 

31-1035  giaini. 

1  lb.  (Avoirdupois)  =  453'5y3 


INDEX 


Acidification  of  milk,  49 
Acidity  of  compound  manures,  38 
Acid-radicals,  examination  for,  71 
Acids  and  alkalies,  12 

—  action  of  lime  on,  29 

—  action  of  milk  on,  49 

—  reactions  for,  61 
Air,  action  on  lime,  29 

—  carbonic  acid  in,  19 

—  experiments  on,  19 

—  water  in,  19 
Albuminoids  in  cheese,  52 

—  in  grass,  44 

—  in  milk,  49 

—  in  oil-cakes,  42 

—  in  turnip  juice,  47 
Alkalies  and  acids,  12 

—  in  grass,  45 

—  in  insoluble  substances,  73 
Aluminium,  tests  for,  55 
Ammoniacal  nitrogen,  test  for,  34,  40 
Ammonia  in  guano,  36 

—  in  water,  25 

—  preparation  of,  18 

—  properties  of,  18 

—  sulphate  of,  37 

Ammonium  citrate,  action  on  phos- 
phate, 32 
action  on  reverted  phosphate,  33 

—  molybdate,  preparation  of,  82 

—  tests  for,  60 

Analysis  of  insoluble  substances,  72 

—  qualitative,  53 

tables  for,  65 

Apparatus,  cleaning  of,  54 

—  for  each  student,  76 

—  for  general  use,  78 

—  for  Sections  I.,  II.,  and  III.,  jj 
Ash  in  grass,  45 

—  in  guano,  36 
Atmospheric  burner,  1 
Atomic  weights,  85 


Bath,  steam,  8 

Bellows,  foot,  3 

Bending  glass  tube  and  rod,  3 

Blowpipe,  2 

—  mouth,  2 
— table,  3 

Bone,  action  of  heat  on,  37 

—  action  of  acid  on,  37 

—  phosphate,  31 
Boracic  acid  in  milk,  50 
Borax  head,  12 

—  in  milk,  50 
Boring  corks,  5 
Bunsen  burner,  1 
Burner,  atmospheric,  1 

—  Bunsen,  1 

—  fish-tail,  4 

Burning  carbon  in  oxygen,  15 

—  sulphur  in  oxygen,  14 
Butter,  51 

—  curd  in,  51 

—  salt  in,  52 

—  water  in,  51 


Cake,  cotton,  44 

—  linseed,  43 
Calcium,  tests  for,  58 
Cane  sugar,  47 

inversion  of,  47 

Carbohydrates  in  oil  cake,  42 
Carbonate,  tests  for,  61 
Carbonates  in  water,  24 
Carbon  dioxide,  in  air,  19 

preparation  of,  16 

properties  of,  17 

—  organic,  test  for,  64 
Cereal  foods,  48 
Cheese,  52 

—  albuminoids  in,  52 

—  fat  in,  52 
Chemical  elements,  85 


INDEX 


89 


Chemicals  and  reagents,  79 

—  for  Sections  I.  and  II.,  80 
Chloride,  tests  for,  62 
Chlorine,  organic,  tests  for,  64 
Chlorophyll,  45 

Clay  in  soils,  26 
Cleaning  apparatus,  54 
Closed  tubes,  4 
Cobalt-blue  glass,  30 
Coloration  of  borax  head,  12 

—  of  flame,  11 
Compound  manures,  38 
Constituents  of  manures,  28 
Cork-borers,  5 

—  boring,  5 
Cotton-cake,  44 
Cotton-wool  in  cotton-cake,  44 
Crystallisation,  8 

Curd  in  butter,  51 
Curdling  of  milk,  49 
Cutting  glass  tube  and  rod,  3 

Dairy  produce,  49 
Decantation,  9 
Distillation  of  water,  22 
Distilled  water,  22 
Drying  precipitates,  10 

Elements,  chemical,  85 
English  weights  and  measures,  86 
Entry  in  note-book,  54,  74 
Evaporation,  7 
Explanation  of  phosphate  table,  70 


Fat  in  cheese,  52 

—  in  milk,  49 

Feeding  materials,  experiments  on,  41 
Fehling's  solution,  preparation  of,  82 
Ferric  salts,  tests  for,  57 
Ferrous  salts,  tests  for,  56 
Fibre,  woody,  in  oil-cakes,  43 
Filter  paper,  9 

—  folding,  9 
Filtration,  9 
Fish-tail  burner,  4 
Fitting  wash-bottle,  5 
Flame  colorations,  11 
Flour,  gluten  in,  48 

—  starch  in,  48 
Folding  filters,  9 
Foot-bellows,  3 
Formalin  in  milk,  5X 
Funnel,  9 

Fusion,  11 


Gas-lime,  sulphur  in,  30 

Glass  rod,  bending  and  cutting,  3 

—  tube,  bending  and  cutting,  3 
Gluten  in  flour,  48 

Grape  sugar,  47 
Grass,  44 

—  albuminoids  in,  44 

—  alkalies  in,  45 

—  ash  in,  45 

—  chlorophyll  in,  45 

—  phosphates  in,  46 

—  phosphoric  acid  in,  45 
Guano,  ammonia  in,  36 

—  ash  in,  36 

—  soluble  phosphates  in,  36 
Gypsum,  sulphur  in,  30 

Hardness  of  water,  24 
Hay,  44 

—  albuminoids  in,  44 

—  alkalies  in,  45 

—  ash  in,  45 

—  chlorophyll  in,  45 

—  phosphoric  acid  in,  45 
Heat,  action  on  bones,  37 
Humus,  nature  of,  28 

—  test  for,  27 

Hydrogen,  preparation  of,  20 

—  properties  of,  21 

Ignition,  ii 

—  tubes,  4 
India-rubber  corks,  5 
Indigo-prism,  preparation  of,  78 
use  of,  11 

Insoluble  phosphate,  test  for,  39 

—  substances,  analysis  of,  72 
Inversion  of  cane  sugar,  47 
Iron,  action  of  lime  on,  30 

—  tests  for,  56 


Juice  in  roots,  46 

Kainit,  potash  in,  31 

Lamp,  spirit,  2 
Leguminous  foods,  48 
Lime,  action  on  acids,  29 

—  action  on  air,  29 

—  action  on  clay,  26 

—  action  on  salts  of  iron,  30 

—  action  on  superphosphate,  33 


90 


PRACTICAL   AGRICULTURAL  CHEMISTRY 


Lime  manures,  28 

—  slaking,  28 

—  in  soil,  27 

—  solubility  of,  29 

—  tests  for,  27 

—  in  water,  23 
Limestone  soils,  27 
Linseed  cake,  43 

adulteration  of,  43 

mucilage  in,  43 

starch  in,  44 

Litmus  paper,  12 
Loam,  26 


Magnesium,  tests  for,  59 
Manganese,  tests  for,  57 
Mangels,  46 
Manures,  acidity  in,  38 

—  compound,  38 

—  experiments  on,  28 

—  lime,  28 

—  mixing,  35 

—  nitrogenous,  33 

—  phosphatic,  31 

—  potash,  31 

—  testing,  36 
Measures,  86 

Metals,  preliminary  examination  for, 
65 

—  reactions  of,  55 

—  separation  of,  68 

—  wet  examination  for,  67 
Metric  weights  and  measures,  86 
Milk,  49 

—  acidification  of,  49 

—  action  of  acids  on,  49 
• —  albuminoids  in,  49 

—  fat  in,  49 

—  preservation  of  preservatives  in,  50 

—  sugar  in,  49 
Mineral  phosphate,  31 
Mixing  manures,  35 
Mounting  platinum  wire,  4 
Mouth  blowpipe,  2 
Mucilage  in  linseed  cake,  43 


Natural  waters,  22 

Nessler's  solution,  preparation  of,  80 

Nitrates,  action  on  superphosphate, 

35 
Nitrate,  test  for,  62 
Nitric  acid,  action  on  phosphates,  32 
—  nitrogen,  34,  40 
Nitrite,  tests  for,  61 


Nitrogen,  ammoniacal,  34 

—  ammoniacal,  test  for,  34,  40 

—  in  albuminoids,  41 

—  in  curd,  51 

—  nitric,  34,  40 

—  nitric,  tests  for,  34,  40 
Nitrogenous  manures,  33 
Nitrogen,  organic,  34 

—  organic,  test  for,  34,  39,  64 

—  preparation  of,  15 

—  properties  of,  16 
Note-book,  54 

—  entry  of  analysis,  74 

Notes  on  separation  of  metals,  67 


Oil-cakes,  41 

—  albuminoids  in,  42 

—  carbohydrates  in,  42 

—  oil  in.  41 

—  sand  in,  43 

—  water  in,  41 

—  woody  fibre  in,  43 
Oil  in  oil-cakes,  41 
Organic  carbon,  test  for,  64 

—  chlorine,  test  for,  64 

—  matter,  test  for,  27 

—  nitrogen,  tests  for,  34,  39,  64 

—  sulphur,  test  for,  65 
Oven,  steam,  10 
Oxygen,  preparation  of,  13 

—  properties  of,  14 


Peat,  26 
Phosphate,  bone,  31 

—  mineral,  31 

Phosphates,    action    of    ammonium 
citrate  on,  32 

—  action  of  dilute  nitric  acid  on,  32 

—  action  of  water  on,  31 

—  in  grass,  46 

—  insoluble,  tests  for,  38,  39 

—  of  lime,  31 

—  soluble,  tests  for,  38 

—  table,  explanation  of,  70 

—  table  for  separation  of,  70 

—  tests  for,  63 
Phosphatic  manures,  31 
Phosphoric  acid,  31 

in  guano,  36 

Platinum  wire  mounting,  4 
Potash  in  kainit,  31 

—  manures,  31 

—  manures,  tests  for,  40 
Potassium,  tests  for,  60 


INDEX 


Precipitates,  drying,  10 

—  washing,  9 

Precipitation,  8 

Preliminary  examination  for  acids,  71 

Preliminary  examination  for  metals, 

65 
Process  of  solution,  67 
Pure  water,  23 


Qualitative,  analysis,  53 
tables  for,  65 


Reactions  for  acid-radicals,  61 

—  for  metals,  55 
Reagents  and  chemicals,  79 

—  for  each  bench,  79 

—  for  the  acids,  83 

—  for  the  metals,  82 
Results,  statement  of,  74 
Reversion  of  superphosphate,  32 
Reverted  phosphate,  31 

action  of  ammonium  citrate  on, 

33 
Roots,  46 

Rose-top  for  bunsen,  2 
Rubber  corks,  5 
Rules  for  working,  54 


Salt  in  butter,  52 

—  in  water,  24 

Sand  and  clay,  separation  of,  26 

—  in  oil-cakes,  43 

—  in  soil,  26 
Separation  of  metals,  68 

notes  on,  67 

Shoddy,  nitrogen  in,  34 
Silicate,  test  for,  63 

Slag,  action  on  sulphate  of  ammonia, 

35    •  u         u 

—  action  on  superphosphate,  35 

—  phosphate,  31 
Slaking  lime,  28 
Sodium,  tests  for,  59 
Softening  corks,  5 
Soil,  limestone  in,  27 
Soils,  experiments  on,  26 
Solids  in  water,  23 
Solubility,  6 

—  of  lime,  29 

—  of  the  phosphates  of  lime,  31 
Soluble  phosphates  in  guano,  36 
test  for,  38 

Solution,  6 


Solution,  chemical,  7 

—  simple,  7 

Solutions  for  reactions  of  acids,  84 

of  metals,  84 

Solvent,  6 
Spirit-lamp,  2 
Starch  in  flour,  48 

—  in  linseed  cake,  44 
Steam  bath,  8 
Steam  oven,  10 
Sublimation,  11 
Substances  for  Section  III.,  81 
Sugar,  cane,  47 

—  grape,  47 

—  in  milk,  49 

—  in  roots,  46 

—  inversion  of,  47 
Sulphate,  in  water,  24 

—  of  ammonia,  action  of  slag  on,  35 

—  of  ammonia,  testing,  37 

—  of  ammonia,  volatility  of,  37 

—  test  for,  61 
Sulphur  in  gas-lime,  30 

—  in  gypsum,  30 

—  organic  test  for,  65 
Superphosphate,  31 

—  action  of  lime  on,  33 

—  action  of  nitrates  on,  35 

—  reversion  of,  32 
Swedes,  46 
Symbols,  85 


Table  blowpipe,  3 

Tables  for  examination  of  acids,  71 

—  for    preliminary  examination    for 
metals,  65 

—  for  qualitative  analysis,  65 

—  for  separation  of  metals,  68 

—  for  separation  of  phosphates,  70 
Test  for  carbon  dioxide,  17 
Testing  manures,  36 

Test  papers,  12 
Thermometric  scales,  85 
Thiocyanates,  37 
Tubes,  closed,  4 

—  ignition,  4 
Turmeric  paper,  12 
Turnips,  46 

—  juice  in,  46 

—  sugar  in,  46 
Turnip-juice,  albuminoids  in,  47 


Volatility  of  sulphate  of  ammonia, 
37 


92 


PRACTICAL  AGRICULTURAL  CHEMISTRY 


Wash  bottle,  5 
Washing  precipitates,  9 

—  precipitates,  by  decantation,  9 
by  filtration,  10 

Water,  action  on  phosphates,  31 

—  ammonia  in,  25 

—  bath,  8 

—  carbonates  in,  24 

—  distillation  of,  22 

—  experiments  on.  22 

—  hardness  of,  24 

—  in  air,  19 


Water,  in  butter,  51 

—  in  oil-cakes,  41 

—  lime  in,  23 

—  natural,  22 

—  salt  in,  24 

—  solids  in,  23 

—  sulphates  in,  24 
Weights,  atomic,  85 
Weights  and  measures,  86 
Wet  examination  for  metals,  67 
Woody  fibre  in  oil-cakes,  43 
Working,  rules  for,  54 


PRINTED  BT 

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